relcache.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * relcache.c
 *    POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/cache/relcache.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *      RelationCacheInitialize         - initialize relcache (to empty)
 *      RelationCacheInitializePhase2   - initialize shared-catalog entries
 *      RelationCacheInitializePhase3   - finish initializing relcache
 *      RelationIdGetRelation           - get a reldesc by relation id
 *      RelationClose                   - close an open relation
 *
 * NOTES
 *      The following code contains many undocumented hacks.  Please be
 *      careful....
 */
#include "postgres.h"
 
#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>
 
#include "access/htup_details.h"
#include "access/multixact.h"
#include "access/parallel.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "access/tableam.h"
#include "access/tupdesc_details.h"
#include "access/xact.h"
#include "catalog/binary_upgrade.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/partition.h"
#include "catalog/pg_am.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_publication.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_shseclabel.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_subscription.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "catalog/schemapg.h"
#include "catalog/storage.h"
#include "commands/policy.h"
#include "commands/publicationcmds.h"
#include "commands/trigger.h"
#include "common/int.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "pgstat.h"
#include "rewrite/rewriteDefine.h"
#include "rewrite/rowsecurity.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/datum.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relmapper.h"
#include "utils/resowner.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
 
#define RELCACHE_INIT_FILEMAGIC     0x573266    /* version ID value */
 
/*
 * Whether to bother checking if relation cache memory needs to be freed
 * eagerly.  See also RelationBuildDesc() and pg_config_manual.h.
 */
#if defined(RECOVER_RELATION_BUILD_MEMORY) && (RECOVER_RELATION_BUILD_MEMORY != 0)
#define MAYBE_RECOVER_RELATION_BUILD_MEMORY 1
#else
#define RECOVER_RELATION_BUILD_MEMORY 0
#ifdef DISCARD_CACHES_ENABLED
#define MAYBE_RECOVER_RELATION_BUILD_MEMORY 1
#endif
#endif
 
/*
 *      hardcoded tuple descriptors, contents generated by genbki.pl
 */
static const FormData_pg_attribute Desc_pg_class[Natts_pg_class] = {Schema_pg_class};
static const FormData_pg_attribute Desc_pg_attribute[Natts_pg_attribute] = {Schema_pg_attribute};
static const FormData_pg_attribute Desc_pg_proc[Natts_pg_proc] = {Schema_pg_proc};
static const FormData_pg_attribute Desc_pg_type[Natts_pg_type] = {Schema_pg_type};
static const FormData_pg_attribute Desc_pg_database[Natts_pg_database] = {Schema_pg_database};
static const FormData_pg_attribute Desc_pg_authid[Natts_pg_authid] = {Schema_pg_authid};
static const FormData_pg_attribute Desc_pg_auth_members[Natts_pg_auth_members] = {Schema_pg_auth_members};
static const FormData_pg_attribute Desc_pg_index[Natts_pg_index] = {Schema_pg_index};
static const FormData_pg_attribute Desc_pg_shseclabel[Natts_pg_shseclabel] = {Schema_pg_shseclabel};
static const FormData_pg_attribute Desc_pg_subscription[Natts_pg_subscription] = {Schema_pg_subscription};
 
/*
 *      Hash tables that index the relation cache
 *
 *      We used to index the cache by both name and OID, but now there
 *      is only an index by OID.
 */
typedef struct relidcacheent
{
    Oid         reloid;
    Relation    reldesc;
} RelIdCacheEnt;
 
static HTAB *RelationIdCache;
 
/*
 * This flag is false until we have prepared the critical relcache entries
 * that are needed to do indexscans on the tables read by relcache building.
 */
bool        criticalRelcachesBuilt = false;
 
/*
 * This flag is false until we have prepared the critical relcache entries
 * for shared catalogs (which are the tables needed for login).
 */
bool        criticalSharedRelcachesBuilt = false;
 
/*
 * This counter counts relcache inval events received since backend startup
 * (but only for rels that are actually in cache).  Presently, we use it only
 * to detect whether data about to be written by write_relcache_init_file()
 * might already be obsolete.
 */
static long relcacheInvalsReceived = 0L;
 
/*
 * in_progress_list is a stack of ongoing RelationBuildDesc() calls.  CREATE
 * INDEX CONCURRENTLY makes catalog changes under ShareUpdateExclusiveLock.
 * It critically relies on each backend absorbing those changes no later than
 * next transaction start.  Hence, RelationBuildDesc() loops until it finishes
 * without accepting a relevant invalidation.  (Most invalidation consumers
 * don't do this.)
 */
typedef struct inprogressent
{
    Oid         reloid;         /* OID of relation being built */
    bool        invalidated;    /* whether an invalidation arrived for it */
} InProgressEnt;
 
static InProgressEnt *in_progress_list;
static int  in_progress_list_len;
static int  in_progress_list_maxlen;
 
/*
 * eoxact_list[] stores the OIDs of relations that (might) need AtEOXact
 * cleanup work.  This list intentionally has limited size; if it overflows,
 * we fall back to scanning the whole hashtable.  There is no value in a very
 * large list because (1) at some point, a hash_seq_search scan is faster than
 * retail lookups, and (2) the value of this is to reduce EOXact work for
 * short transactions, which can't have dirtied all that many tables anyway.
 * EOXactListAdd() does not bother to prevent duplicate list entries, so the
 * cleanup processing must be idempotent.
 */
#define MAX_EOXACT_LIST 32
static Oid  eoxact_list[MAX_EOXACT_LIST];
static int  eoxact_list_len = 0;
static bool eoxact_list_overflowed = false;
 
#define EOXactListAdd(rel) \
    do { \
        if (eoxact_list_len < MAX_EOXACT_LIST) \
            eoxact_list[eoxact_list_len++] = (rel)->rd_id; \
        else \
            eoxact_list_overflowed = true; \
    } while (0)
 
/*
 * EOXactTupleDescArray stores TupleDescs that (might) need AtEOXact
 * cleanup work.  The array expands as needed; there is no hashtable because
 * we don't need to access individual items except at EOXact.
 */
static TupleDesc *EOXactTupleDescArray;
static int  NextEOXactTupleDescNum = 0;
static int  EOXactTupleDescArrayLen = 0;
 
/*
 *      macros to manipulate the lookup hashtable
 */
#define RelationCacheInsert(RELATION, replace_allowed)  \
do { \
    RelIdCacheEnt *hentry; bool found; \
    hentry = (RelIdCacheEnt *) hash_search(RelationIdCache, \
                                           &((RELATION)->rd_id), \
                                           HASH_ENTER, &found); \
    if (found) \
    { \
        /* see comments in RelationBuildDesc and RelationBuildLocalRelation */ \
        Relation _old_rel = hentry->reldesc; \
        Assert(replace_allowed); \
        hentry->reldesc = (RELATION); \
        if (RelationHasReferenceCountZero(_old_rel)) \
            RelationDestroyRelation(_old_rel, false); \
        else if (!IsBootstrapProcessingMode()) \
            elog(WARNING, "leaking still-referenced relcache entry for \"%s\"", \
                 RelationGetRelationName(_old_rel)); \
    } \
    else \
        hentry->reldesc = (RELATION); \
} while(0)
 
#define RelationIdCacheLookup(ID, RELATION) \
do { \
    RelIdCacheEnt *hentry; \
    hentry = (RelIdCacheEnt *) hash_search(RelationIdCache, \
                                           &(ID), \
                                           HASH_FIND, NULL); \
    if (hentry) \
        RELATION = hentry->reldesc; \
    else \
        RELATION = NULL; \
} while(0)
 
#define RelationCacheDelete(RELATION) \
do { \
    RelIdCacheEnt *hentry; \
    hentry = (RelIdCacheEnt *) hash_search(RelationIdCache, \
                                           &((RELATION)->rd_id), \
                                           HASH_REMOVE, NULL); \
    if (hentry == NULL) \
        elog(WARNING, "failed to delete relcache entry for OID %u", \
             (RELATION)->rd_id); \
} while(0)
 
 
/*
 * Special cache for opclass-related information
 *
 * Note: only default support procs get cached, ie, those with
 * lefttype = righttype = opcintype.
 */
typedef struct opclasscacheent
{
    Oid         opclassoid;     /* lookup key: OID of opclass */
    bool        valid;          /* set true after successful fill-in */
    StrategyNumber numSupport;  /* max # of support procs (from pg_am) */
    Oid         opcfamily;      /* OID of opclass's family */
    Oid         opcintype;      /* OID of opclass's declared input type */
    RegProcedure *supportProcs; /* OIDs of support procedures */
} OpClassCacheEnt;
 
static HTAB *OpClassCache = NULL;
 
 
/* non-export function prototypes */
 
static void RelationCloseCleanup(Relation relation);
static void RelationDestroyRelation(Relation relation, bool remember_tupdesc);
static void RelationInvalidateRelation(Relation relation);
static void RelationClearRelation(Relation relation);
static void RelationRebuildRelation(Relation relation);
 
static void RelationReloadIndexInfo(Relation relation);
static void RelationReloadNailed(Relation relation);
static void RelationFlushRelation(Relation relation);
static void RememberToFreeTupleDescAtEOX(TupleDesc td);
#ifdef USE_ASSERT_CHECKING
static void AssertPendingSyncConsistency(Relation relation);
#endif
static void AtEOXact_cleanup(Relation relation, bool isCommit);
static void AtEOSubXact_cleanup(Relation relation, bool isCommit,
                                SubTransactionId mySubid, SubTransactionId parentSubid);
static bool load_relcache_init_file(bool shared);
static void write_relcache_init_file(bool shared);
static void write_item(const void *data, Size len, FILE *fp);
 
static void formrdesc(const char *relationName, Oid relationReltype,
                      bool isshared, int natts, const FormData_pg_attribute *attrs);
 
static HeapTuple ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic);
static Relation AllocateRelationDesc(Form_pg_class relp);
static void RelationParseRelOptions(Relation relation, HeapTuple tuple);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, bool insertIt);
static void RelationInitPhysicalAddr(Relation relation);
static void load_critical_index(Oid indexoid, Oid heapoid);
static TupleDesc GetPgClassDescriptor(void);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation, int ndef);
static int  AttrDefaultCmp(const void *a, const void *b);
static void CheckConstraintFetch(Relation relation);
static int  CheckConstraintCmp(const void *a, const void *b);
static void InitIndexAmRoutine(Relation relation);
static void IndexSupportInitialize(oidvector *indclass,
                                   RegProcedure *indexSupport,
                                   Oid *opFamily,
                                   Oid *opcInType,
                                   StrategyNumber maxSupportNumber,
                                   AttrNumber maxAttributeNumber);
static OpClassCacheEnt *LookupOpclassInfo(Oid operatorClassOid,
                                          StrategyNumber numSupport);
static void RelationCacheInitFileRemoveInDir(const char *tblspcpath);
static void unlink_initfile(const char *initfilename, int elevel);
 
 
/*
 *      ScanPgRelation
 *
 *      This is used by RelationBuildDesc to find a pg_class
 *      tuple matching targetRelId.  The caller must hold at least
 *      AccessShareLock on the target relid to prevent concurrent-update
 *      scenarios; it isn't guaranteed that all scans used to build the
 *      relcache entry will use the same snapshot.  If, for example,
 *      an attribute were to be added after scanning pg_class and before
 *      scanning pg_attribute, relnatts wouldn't match.
 *
 *      NB: the returned tuple has been copied into palloc'd storage
 *      and must eventually be freed with heap_freetuple.
 */
static HeapTuple
ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic)
{
    HeapTuple   pg_class_tuple;
    Relation    pg_class_desc;
    SysScanDesc pg_class_scan;
    ScanKeyData key[1];
    Snapshot    snapshot = NULL;
 
    /*
     * If something goes wrong during backend startup, we might find ourselves
     * trying to read pg_class before we've selected a database.  That ain't
     * gonna work, so bail out with a useful error message.  If this happens,
     * it probably means a relcache entry that needs to be nailed isn't.
     */
    if (!OidIsValid(MyDatabaseId))
        elog(FATAL, "cannot read pg_class without having selected a database");
 
    /*
     * form a scan key
     */
    ScanKeyInit(&key[0],
                Anum_pg_class_oid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(targetRelId));
 
    /*
     * Open pg_class and fetch a tuple.  Force heap scan if we haven't yet
     * built the critical relcache entries (this includes initdb and startup
     * without a pg_internal.init file).  The caller can also force a heap
     * scan by setting indexOK == false.
     */
    pg_class_desc = table_open(RelationRelationId, AccessShareLock);
 
    /*
     * The caller might need a tuple that's newer than the one the historic
     * snapshot; currently the only case requiring to do so is looking up the
     * relfilenumber of non mapped system relations during decoding. That
     * snapshot can't change in the midst of a relcache build, so there's no
     * need to register the snapshot.
     */
    if (force_non_historic)
        snapshot = GetNonHistoricCatalogSnapshot(RelationRelationId);
 
    pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
                                       indexOK && criticalRelcachesBuilt,
                                       snapshot,
                                       1, key);
 
    pg_class_tuple = systable_getnext(pg_class_scan);
 
    /*
     * Must copy tuple before releasing buffer.
     */
    if (HeapTupleIsValid(pg_class_tuple))
        pg_class_tuple = heap_copytuple(pg_class_tuple);
 
    /* all done */
    systable_endscan(pg_class_scan);
    table_close(pg_class_desc, AccessShareLock);
 
    return pg_class_tuple;
}
 
/*
 *      AllocateRelationDesc
 *
 *      This is used to allocate memory for a new relation descriptor
 *      and initialize the rd_rel field from the given pg_class tuple.
 */
static Relation
AllocateRelationDesc(Form_pg_class relp)
{
    Relation    relation;
    MemoryContext oldcxt;
    Form_pg_class relationForm;
 
    /* Relcache entries must live in CacheMemoryContext */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
    /*
     * allocate and zero space for new relation descriptor
     */
    relation = (Relation) palloc0(sizeof(RelationData));
 
    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;
 
    /*
     * Copy the relation tuple form
     *
     * We only allocate space for the fixed fields, ie, CLASS_TUPLE_SIZE. The
     * variable-length fields (relacl, reloptions) are NOT stored in the
     * relcache --- there'd be little point in it, since we don't copy the
     * tuple's nulls bitmap and hence wouldn't know if the values are valid.
     * Bottom line is that relacl *cannot* be retrieved from the relcache. Get
     * it from the syscache if you need it.  The same goes for the original
     * form of reloptions (however, we do store the parsed form of reloptions
     * in rd_options).
     */
    relationForm = (Form_pg_class) palloc(CLASS_TUPLE_SIZE);
 
    memcpy(relationForm, relp, CLASS_TUPLE_SIZE);
 
    /* initialize relation tuple form */
    relation->rd_rel = relationForm;
 
    /* and allocate attribute tuple form storage */
    relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts);
    /* which we mark as a reference-counted tupdesc */
    relation->rd_att->tdrefcount = 1;
 
    MemoryContextSwitchTo(oldcxt);
 
    return relation;
}
 
/*
 * RelationParseRelOptions
 *      Convert pg_class.reloptions into pre-parsed rd_options
 *
 * tuple is the real pg_class tuple (not rd_rel!) for relation
 *
 * Note: rd_rel and (if an index) rd_indam must be valid already
 */
static void
RelationParseRelOptions(Relation relation, HeapTuple tuple)
{
    bytea      *options;
    amoptions_function amoptsfn;
 
    relation->rd_options = NULL;
 
    /*
     * Look up any AM-specific parse function; fall out if relkind should not
     * have options.
     */
    switch (relation->rd_rel->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_TOASTVALUE:
        case RELKIND_VIEW:
        case RELKIND_MATVIEW:
        case RELKIND_PARTITIONED_TABLE:
            amoptsfn = NULL;
            break;
        case RELKIND_INDEX:
        case RELKIND_PARTITIONED_INDEX:
            amoptsfn = relation->rd_indam->amoptions;
            break;
        default:
            return;
    }
 
    /*
     * Fetch reloptions from tuple; have to use a hardwired descriptor because
     * we might not have any other for pg_class yet (consider executing this
     * code for pg_class itself)
     */
    options = extractRelOptions(tuple, GetPgClassDescriptor(), amoptsfn);
 
    /*
     * Copy parsed data into CacheMemoryContext.  To guard against the
     * possibility of leaks in the reloptions code, we want to do the actual
     * parsing in the caller's memory context and copy the results into
     * CacheMemoryContext after the fact.
     */
    if (options)
    {
        relation->rd_options = MemoryContextAlloc(CacheMemoryContext,
                                                  VARSIZE(options));
        memcpy(relation->rd_options, options, VARSIZE(options));
        pfree(options);
    }
}
 
/*
 *      RelationBuildTupleDesc
 *
 *      Form the relation's tuple descriptor from information in
 *      the pg_attribute, pg_attrdef & pg_constraint system catalogs.
 */
static void
RelationBuildTupleDesc(Relation relation)
{
    HeapTuple   pg_attribute_tuple;
    Relation    pg_attribute_desc;
    SysScanDesc pg_attribute_scan;
    ScanKeyData skey[2];
    int         need;
    TupleConstr *constr;
    AttrMissing *attrmiss = NULL;
    int         ndef = 0;
 
    /* fill rd_att's type ID fields (compare heap.c's AddNewRelationTuple) */
    relation->rd_att->tdtypeid =
        relation->rd_rel->reltype ? relation->rd_rel->reltype : RECORDOID;
    relation->rd_att->tdtypmod = -1;    /* just to be sure */
 
    constr = (TupleConstr *) MemoryContextAllocZero(CacheMemoryContext,
                                                    sizeof(TupleConstr));
 
    /*
     * Form a scan key that selects only user attributes (attnum > 0).
     * (Eliminating system attribute rows at the index level is lots faster
     * than fetching them.)
     */
    ScanKeyInit(&skey[0],
                Anum_pg_attribute_attrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
    ScanKeyInit(&skey[1],
                Anum_pg_attribute_attnum,
                BTGreaterStrategyNumber, F_INT2GT,
                Int16GetDatum(0));
 
    /*
     * Open pg_attribute and begin a scan.  Force heap scan if we haven't yet
     * built the critical relcache entries (this includes initdb and startup
     * without a pg_internal.init file).
     */
    pg_attribute_desc = table_open(AttributeRelationId, AccessShareLock);
    pg_attribute_scan = systable_beginscan(pg_attribute_desc,
                                           AttributeRelidNumIndexId,
                                           criticalRelcachesBuilt,
                                           NULL,
                                           2, skey);
 
    /*
     * add attribute data to relation->rd_att
     */
    need = RelationGetNumberOfAttributes(relation);
 
    while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
    {
        Form_pg_attribute attp;
        int         attnum;
 
        attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);
 
        attnum = attp->attnum;
        if (attnum <= 0 || attnum > RelationGetNumberOfAttributes(relation))
            elog(ERROR, "invalid attribute number %d for relation \"%s\"",
                 attp->attnum, RelationGetRelationName(relation));
 
        memcpy(TupleDescAttr(relation->rd_att, attnum - 1),
               attp,
               ATTRIBUTE_FIXED_PART_SIZE);
 
        populate_compact_attribute(relation->rd_att, attnum - 1);
 
        /* Update constraint/default info */
        if (attp->attnotnull)
            constr->has_not_null = true;
        if (attp->attgenerated == ATTRIBUTE_GENERATED_STORED)
            constr->has_generated_stored = true;
        if (attp->atthasdef)
            ndef++;
 
        /* If the column has a "missing" value, put it in the attrmiss array */
        if (attp->atthasmissing)
        {
            Datum       missingval;
            bool        missingNull;
 
            /* Do we have a missing value? */
            missingval = heap_getattr(pg_attribute_tuple,
                                      Anum_pg_attribute_attmissingval,
                                      pg_attribute_desc->rd_att,
                                      &missingNull);
            if (!missingNull)
            {
                /* Yes, fetch from the array */
                MemoryContext oldcxt;
                bool        is_null;
                int         one = 1;
                Datum       missval;
 
                if (attrmiss == NULL)
                    attrmiss = (AttrMissing *)
                        MemoryContextAllocZero(CacheMemoryContext,
                                               relation->rd_rel->relnatts *
                                               sizeof(AttrMissing));
 
                missval = array_get_element(missingval,
                                            1,
                                            &one,
                                            -1,
                                            attp->attlen,
                                            attp->attbyval,
                                            attp->attalign,
                                            &is_null);
                Assert(!is_null);
                if (attp->attbyval)
                {
                    /* for copy by val just copy the datum direct */
                    attrmiss[attnum - 1].am_value = missval;
                }
                else
                {
                    /* otherwise copy in the correct context */
                    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
                    attrmiss[attnum - 1].am_value = datumCopy(missval,
                                                              attp->attbyval,
                                                              attp->attlen);
                    MemoryContextSwitchTo(oldcxt);
                }
                attrmiss[attnum - 1].am_present = true;
            }
        }
        need--;
        if (need == 0)
            break;
    }
 
    /*
     * end the scan and close the attribute relation
     */
    systable_endscan(pg_attribute_scan);
    table_close(pg_attribute_desc, AccessShareLock);
 
    if (need != 0)
        elog(ERROR, "pg_attribute catalog is missing %d attribute(s) for relation OID %u",
             need, RelationGetRelid(relation));
 
    /*
     * We can easily set the attcacheoff value for the first attribute: it
     * must be zero.  This eliminates the need for special cases for attnum=1
     * that used to exist in fastgetattr() and index_getattr().
     */
    if (RelationGetNumberOfAttributes(relation) > 0)
        TupleDescCompactAttr(relation->rd_att, 0)->attcacheoff = 0;
 
    /*
     * Set up constraint/default info
     */
    if (constr->has_not_null ||
        constr->has_generated_stored ||
        ndef > 0 ||
        attrmiss ||
        relation->rd_rel->relchecks > 0)
    {
        relation->rd_att->constr = constr;
 
        if (ndef > 0)           /* DEFAULTs */
            AttrDefaultFetch(relation, ndef);
        else
            constr->num_defval = 0;
 
        constr->missing = attrmiss;
 
        if (relation->rd_rel->relchecks > 0)    /* CHECKs */
            CheckConstraintFetch(relation);
        else
            constr->num_check = 0;
    }
    else
    {
        pfree(constr);
        relation->rd_att->constr = NULL;
    }
}
 
/*
 *      RelationBuildRuleLock
 *
 *      Form the relation's rewrite rules from information in
 *      the pg_rewrite system catalog.
 *
 * Note: The rule parsetrees are potentially very complex node structures.
 * To allow these trees to be freed when the relcache entry is flushed,
 * we make a private memory context to hold the RuleLock information for
 * each relcache entry that has associated rules.  The context is used
 * just for rule info, not for any other subsidiary data of the relcache
 * entry, because that keeps the update logic in RelationRebuildRelation()
 * manageable.  The other subsidiary data structures are simple enough
 * to be easy to free explicitly, anyway.
 *
 * Note: The relation's reloptions must have been extracted first.
 */
static void
RelationBuildRuleLock(Relation relation)
{
    MemoryContext rulescxt;
    MemoryContext oldcxt;
    HeapTuple   rewrite_tuple;
    Relation    rewrite_desc;
    TupleDesc   rewrite_tupdesc;
    SysScanDesc rewrite_scan;
    ScanKeyData key;
    RuleLock   *rulelock;
    int         numlocks;
    RewriteRule **rules;
    int         maxlocks;
 
    /*
     * Make the private context.  Assume it'll not contain much data.
     */
    rulescxt = AllocSetContextCreate(CacheMemoryContext,
                                     "relation rules",
                                     ALLOCSET_SMALL_SIZES);
    relation->rd_rulescxt = rulescxt;
    MemoryContextCopyAndSetIdentifier(rulescxt,
                                      RelationGetRelationName(relation));
 
    /*
     * allocate an array to hold the rewrite rules (the array is extended if
     * necessary)
     */
    maxlocks = 4;
    rules = (RewriteRule **)
        MemoryContextAlloc(rulescxt, sizeof(RewriteRule *) * maxlocks);
    numlocks = 0;
 
    /*
     * form a scan key
     */
    ScanKeyInit(&key,
                Anum_pg_rewrite_ev_class,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    /*
     * open pg_rewrite and begin a scan
     *
     * Note: since we scan the rules using RewriteRelRulenameIndexId, we will
     * be reading the rules in name order, except possibly during
     * emergency-recovery operations (ie, IgnoreSystemIndexes). This in turn
     * ensures that rules will be fired in name order.
     */
    rewrite_desc = table_open(RewriteRelationId, AccessShareLock);
    rewrite_tupdesc = RelationGetDescr(rewrite_desc);
    rewrite_scan = systable_beginscan(rewrite_desc,
                                      RewriteRelRulenameIndexId,
                                      true, NULL,
                                      1, &key);
 
    while (HeapTupleIsValid(rewrite_tuple = systable_getnext(rewrite_scan)))
    {
        Form_pg_rewrite rewrite_form = (Form_pg_rewrite) GETSTRUCT(rewrite_tuple);
        bool        isnull;
        Datum       rule_datum;
        char       *rule_str;
        RewriteRule *rule;
        Oid         check_as_user;
 
        rule = (RewriteRule *) MemoryContextAlloc(rulescxt,
                                                  sizeof(RewriteRule));
 
        rule->ruleId = rewrite_form->oid;
 
        rule->event = rewrite_form->ev_type - '0';
        rule->enabled = rewrite_form->ev_enabled;
        rule->isInstead = rewrite_form->is_instead;
 
        /*
         * Must use heap_getattr to fetch ev_action and ev_qual.  Also, the
         * rule strings are often large enough to be toasted.  To avoid
         * leaking memory in the caller's context, do the detoasting here so
         * we can free the detoasted version.
         */
        rule_datum = heap_getattr(rewrite_tuple,
                                  Anum_pg_rewrite_ev_action,
                                  rewrite_tupdesc,
                                  &isnull);
        Assert(!isnull);
        rule_str = TextDatumGetCString(rule_datum);
        oldcxt = MemoryContextSwitchTo(rulescxt);
        rule->actions = (List *) stringToNode(rule_str);
        MemoryContextSwitchTo(oldcxt);
        pfree(rule_str);
 
        rule_datum = heap_getattr(rewrite_tuple,
                                  Anum_pg_rewrite_ev_qual,
                                  rewrite_tupdesc,
                                  &isnull);
        Assert(!isnull);
        rule_str = TextDatumGetCString(rule_datum);
        oldcxt = MemoryContextSwitchTo(rulescxt);
        rule->qual = (Node *) stringToNode(rule_str);
        MemoryContextSwitchTo(oldcxt);
        pfree(rule_str);
 
        /*
         * If this is a SELECT rule defining a view, and the view has
         * "security_invoker" set, we must perform all permissions checks on
         * relations referred to by the rule as the invoking user.
         *
         * In all other cases (including non-SELECT rules on security invoker
         * views), perform the permissions checks as the relation owner.
         */
        if (rule->event == CMD_SELECT &&
            relation->rd_rel->relkind == RELKIND_VIEW &&
            RelationHasSecurityInvoker(relation))
            check_as_user = InvalidOid;
        else
            check_as_user = relation->rd_rel->relowner;
 
        /*
         * Scan through the rule's actions and set the checkAsUser field on
         * all RTEPermissionInfos. We have to look at the qual as well, in
         * case it contains sublinks.
         *
         * The reason for doing this when the rule is loaded, rather than when
         * it is stored, is that otherwise ALTER TABLE OWNER would have to
         * grovel through stored rules to update checkAsUser fields. Scanning
         * the rule tree during load is relatively cheap (compared to
         * constructing it in the first place), so we do it here.
         */
        setRuleCheckAsUser((Node *) rule->actions, check_as_user);
        setRuleCheckAsUser(rule->qual, check_as_user);
 
        if (numlocks >= maxlocks)
        {
            maxlocks *= 2;
            rules = (RewriteRule **)
                repalloc(rules, sizeof(RewriteRule *) * maxlocks);
        }
        rules[numlocks++] = rule;
    }
 
    /*
     * end the scan and close the attribute relation
     */
    systable_endscan(rewrite_scan);
    table_close(rewrite_desc, AccessShareLock);
 
    /*
     * there might not be any rules (if relhasrules is out-of-date)
     */
    if (numlocks == 0)
    {
        relation->rd_rules = NULL;
        relation->rd_rulescxt = NULL;
        MemoryContextDelete(rulescxt);
        return;
    }
 
    /*
     * form a RuleLock and insert into relation
     */
    rulelock = (RuleLock *) MemoryContextAlloc(rulescxt, sizeof(RuleLock));
    rulelock->numLocks = numlocks;
    rulelock->rules = rules;
 
    relation->rd_rules = rulelock;
}
 
/*
 *      equalRuleLocks
 *
 *      Determine whether two RuleLocks are equivalent
 *
 *      Probably this should be in the rules code someplace...
 */
static bool
equalRuleLocks(RuleLock *rlock1, RuleLock *rlock2)
{
    int         i;
 
    /*
     * As of 7.3 we assume the rule ordering is repeatable, because
     * RelationBuildRuleLock should read 'em in a consistent order.  So just
     * compare corresponding slots.
     */
    if (rlock1 != NULL)
    {
        if (rlock2 == NULL)
            return false;
        if (rlock1->numLocks != rlock2->numLocks)
            return false;
        for (i = 0; i < rlock1->numLocks; i++)
        {
            RewriteRule *rule1 = rlock1->rules[i];
            RewriteRule *rule2 = rlock2->rules[i];
 
            if (rule1->ruleId != rule2->ruleId)
                return false;
            if (rule1->event != rule2->event)
                return false;
            if (rule1->enabled != rule2->enabled)
                return false;
            if (rule1->isInstead != rule2->isInstead)
                return false;
            if (!equal(rule1->qual, rule2->qual))
                return false;
            if (!equal(rule1->actions, rule2->actions))
                return false;
        }
    }
    else if (rlock2 != NULL)
        return false;
    return true;
}
 
/*
 *      equalPolicy
 *
 *      Determine whether two policies are equivalent
 */
static bool
equalPolicy(RowSecurityPolicy *policy1, RowSecurityPolicy *policy2)
{
    int         i;
    Oid        *r1,
               *r2;
 
    if (policy1 != NULL)
    {
        if (policy2 == NULL)
            return false;
 
        if (policy1->polcmd != policy2->polcmd)
            return false;
        if (policy1->hassublinks != policy2->hassublinks)
            return false;
        if (strcmp(policy1->policy_name, policy2->policy_name) != 0)
            return false;
        if (ARR_DIMS(policy1->roles)[0] != ARR_DIMS(policy2->roles)[0])
            return false;
 
        r1 = (Oid *) ARR_DATA_PTR(policy1->roles);
        r2 = (Oid *) ARR_DATA_PTR(policy2->roles);
 
        for (i = 0; i < ARR_DIMS(policy1->roles)[0]; i++)
        {
            if (r1[i] != r2[i])
                return false;
        }
 
        if (!equal(policy1->qual, policy2->qual))
            return false;
        if (!equal(policy1->with_check_qual, policy2->with_check_qual))
            return false;
    }
    else if (policy2 != NULL)
        return false;
 
    return true;
}
 
/*
 *      equalRSDesc
 *
 *      Determine whether two RowSecurityDesc's are equivalent
 */
static bool
equalRSDesc(RowSecurityDesc *rsdesc1, RowSecurityDesc *rsdesc2)
{
    ListCell   *lc,
               *rc;
 
    if (rsdesc1 == NULL && rsdesc2 == NULL)
        return true;
 
    if ((rsdesc1 != NULL && rsdesc2 == NULL) ||
        (rsdesc1 == NULL && rsdesc2 != NULL))
        return false;
 
    if (list_length(rsdesc1->policies) != list_length(rsdesc2->policies))
        return false;
 
    /* RelationBuildRowSecurity should build policies in order */
    forboth(lc, rsdesc1->policies, rc, rsdesc2->policies)
    {
        RowSecurityPolicy *l = (RowSecurityPolicy *) lfirst(lc);
        RowSecurityPolicy *r = (RowSecurityPolicy *) lfirst(rc);
 
        if (!equalPolicy(l, r))
            return false;
    }
 
    return true;
}
 
/*
 *      RelationBuildDesc
 *
 *      Build a relation descriptor.  The caller must hold at least
 *      AccessShareLock on the target relid.
 *
 *      The new descriptor is inserted into the hash table if insertIt is true.
 *
 *      Returns NULL if no pg_class row could be found for the given relid
 *      (suggesting we are trying to access a just-deleted relation).
 *      Any other error is reported via elog.
 */
static Relation
RelationBuildDesc(Oid targetRelId, bool insertIt)
{
    int         in_progress_offset;
    Relation    relation;
    Oid         relid;
    HeapTuple   pg_class_tuple;
    Form_pg_class relp;
 
    /*
     * This function and its subroutines can allocate a good deal of transient
     * data in CurrentMemoryContext.  Traditionally we've just leaked that
     * data, reasoning that the caller's context is at worst of transaction
     * scope, and relcache loads shouldn't happen so often that it's essential
     * to recover transient data before end of statement/transaction.  However
     * that's definitely not true when debug_discard_caches is active, and
     * perhaps it's not true in other cases.
     *
     * When debug_discard_caches is active or when forced to by
     * RECOVER_RELATION_BUILD_MEMORY=1, arrange to allocate the junk in a
     * temporary context that we'll free before returning.  Make it a child of
     * caller's context so that it will get cleaned up appropriately if we
     * error out partway through.
     */
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
    MemoryContext tmpcxt = NULL;
    MemoryContext oldcxt = NULL;
 
    if (RECOVER_RELATION_BUILD_MEMORY || debug_discard_caches > 0)
    {
        tmpcxt = AllocSetContextCreate(CurrentMemoryContext,
                                       "RelationBuildDesc workspace",
                                       ALLOCSET_DEFAULT_SIZES);
        oldcxt = MemoryContextSwitchTo(tmpcxt);
    }
#endif
 
    /* Register to catch invalidation messages */
    if (in_progress_list_len >= in_progress_list_maxlen)
    {
        int         allocsize;
 
        allocsize = in_progress_list_maxlen * 2;
        in_progress_list = repalloc(in_progress_list,
                                    allocsize * sizeof(*in_progress_list));
        in_progress_list_maxlen = allocsize;
    }
    in_progress_offset = in_progress_list_len++;
    in_progress_list[in_progress_offset].reloid = targetRelId;
retry:
    in_progress_list[in_progress_offset].invalidated = false;
 
    /*
     * find the tuple in pg_class corresponding to the given relation id
     */
    pg_class_tuple = ScanPgRelation(targetRelId, true, false);
 
    /*
     * if no such tuple exists, return NULL
     */
    if (!HeapTupleIsValid(pg_class_tuple))
    {
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
        if (tmpcxt)
        {
            /* Return to caller's context, and blow away the temporary context */
            MemoryContextSwitchTo(oldcxt);
            MemoryContextDelete(tmpcxt);
        }
#endif
        Assert(in_progress_offset + 1 == in_progress_list_len);
        in_progress_list_len--;
        return NULL;
    }
 
    /*
     * get information from the pg_class_tuple
     */
    relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
    relid = relp->oid;
    Assert(relid == targetRelId);
 
    /*
     * allocate storage for the relation descriptor, and copy pg_class_tuple
     * to relation->rd_rel.
     */
    relation = AllocateRelationDesc(relp);
 
    /*
     * initialize the relation's relation id (relation->rd_id)
     */
    RelationGetRelid(relation) = relid;
 
    /*
     * Normal relations are not nailed into the cache.  Since we don't flush
     * new relations, it won't be new.  It could be temp though.
     */
    relation->rd_refcnt = 0;
    relation->rd_isnailed = false;
    relation->rd_createSubid = InvalidSubTransactionId;
    relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_droppedSubid = InvalidSubTransactionId;
    switch (relation->rd_rel->relpersistence)
    {
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            relation->rd_backend = INVALID_PROC_NUMBER;
            relation->rd_islocaltemp = false;
            break;
        case RELPERSISTENCE_TEMP:
            if (isTempOrTempToastNamespace(relation->rd_rel->relnamespace))
            {
                relation->rd_backend = ProcNumberForTempRelations();
                relation->rd_islocaltemp = true;
            }
            else
            {
                /*
                 * If it's a temp table, but not one of ours, we have to use
                 * the slow, grotty method to figure out the owning backend.
                 *
                 * Note: it's possible that rd_backend gets set to
                 * MyProcNumber here, in case we are looking at a pg_class
                 * entry left over from a crashed backend that coincidentally
                 * had the same ProcNumber we're using.  We should *not*
                 * consider such a table to be "ours"; this is why we need the
                 * separate rd_islocaltemp flag.  The pg_class entry will get
                 * flushed if/when we clean out the corresponding temp table
                 * namespace in preparation for using it.
                 */
                relation->rd_backend =
                    GetTempNamespaceProcNumber(relation->rd_rel->relnamespace);
                Assert(relation->rd_backend != INVALID_PROC_NUMBER);
                relation->rd_islocaltemp = false;
            }
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c",
                 relation->rd_rel->relpersistence);
            break;
    }
 
    /*
     * initialize the tuple descriptor (relation->rd_att).
     */
    RelationBuildTupleDesc(relation);
 
    /* foreign key data is not loaded till asked for */
    relation->rd_fkeylist = NIL;
    relation->rd_fkeyvalid = false;
 
    /* partitioning data is not loaded till asked for */
    relation->rd_partkey = NULL;
    relation->rd_partkeycxt = NULL;
    relation->rd_partdesc = NULL;
    relation->rd_partdesc_nodetached = NULL;
    relation->rd_partdesc_nodetached_xmin = InvalidTransactionId;
    relation->rd_pdcxt = NULL;
    relation->rd_pddcxt = NULL;
    relation->rd_partcheck = NIL;
    relation->rd_partcheckvalid = false;
    relation->rd_partcheckcxt = NULL;
 
    /*
     * initialize access method information
     */
    if (relation->rd_rel->relkind == RELKIND_INDEX ||
        relation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
        RelationInitIndexAccessInfo(relation);
    else if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind) ||
             relation->rd_rel->relkind == RELKIND_SEQUENCE)
        RelationInitTableAccessMethod(relation);
    else if (relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
    {
        /*
         * Do nothing: access methods are a setting that partitions can
         * inherit.
         */
    }
    else
        Assert(relation->rd_rel->relam == InvalidOid);
 
    /* extract reloptions if any */
    RelationParseRelOptions(relation, pg_class_tuple);
 
    /*
     * Fetch rules and triggers that affect this relation.
     *
     * Note that RelationBuildRuleLock() relies on this being done after
     * extracting the relation's reloptions.
     */
    if (relation->rd_rel->relhasrules)
        RelationBuildRuleLock(relation);
    else
    {
        relation->rd_rules = NULL;
        relation->rd_rulescxt = NULL;
    }
 
    if (relation->rd_rel->relhastriggers)
        RelationBuildTriggers(relation);
    else
        relation->trigdesc = NULL;
 
    if (relation->rd_rel->relrowsecurity)
        RelationBuildRowSecurity(relation);
    else
        relation->rd_rsdesc = NULL;
 
    /*
     * initialize the relation lock manager information
     */
    RelationInitLockInfo(relation); /* see lmgr.c */
 
    /*
     * initialize physical addressing information for the relation
     */
    RelationInitPhysicalAddr(relation);
 
    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;
 
    /*
     * now we can free the memory allocated for pg_class_tuple
     */
    heap_freetuple(pg_class_tuple);
 
    /*
     * If an invalidation arrived mid-build, start over.  Between here and the
     * end of this function, don't add code that does or reasonably could read
     * system catalogs.  That range must be free from invalidation processing
     * for the !insertIt case.  For the insertIt case, RelationCacheInsert()
     * will enroll this relation in ordinary relcache invalidation processing,
     */
    if (in_progress_list[in_progress_offset].invalidated)
    {
        RelationDestroyRelation(relation, false);
        goto retry;
    }
    Assert(in_progress_offset + 1 == in_progress_list_len);
    in_progress_list_len--;
 
    /*
     * Insert newly created relation into relcache hash table, if requested.
     *
     * There is one scenario in which we might find a hashtable entry already
     * present, even though our caller failed to find it: if the relation is a
     * system catalog or index that's used during relcache load, we might have
     * recursively created the same relcache entry during the preceding steps.
     * So allow RelationCacheInsert to delete any already-present relcache
     * entry for the same OID.  The already-present entry should have refcount
     * zero (else somebody forgot to close it); in the event that it doesn't,
     * we'll elog a WARNING and leak the already-present entry.
     */
    if (insertIt)
        RelationCacheInsert(relation, true);
 
    /* It's fully valid */
    relation->rd_isvalid = true;
 
#ifdef MAYBE_RECOVER_RELATION_BUILD_MEMORY
    if (tmpcxt)
    {
        /* Return to caller's context, and blow away the temporary context */
        MemoryContextSwitchTo(oldcxt);
        MemoryContextDelete(tmpcxt);
    }
#endif
 
    return relation;
}
 
/*
 * Initialize the physical addressing info (RelFileLocator) for a relcache entry
 *
 * Note: at the physical level, relations in the pg_global tablespace must
 * be treated as shared, even if relisshared isn't set.  Hence we do not
 * look at relisshared here.
 */
static void
RelationInitPhysicalAddr(Relation relation)
{
    RelFileNumber oldnumber = relation->rd_locator.relNumber;
 
    /* these relations kinds never have storage */
    if (!RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
        return;
 
    if (relation->rd_rel->reltablespace)
        relation->rd_locator.spcOid = relation->rd_rel->reltablespace;
    else
        relation->rd_locator.spcOid = MyDatabaseTableSpace;
    if (relation->rd_locator.spcOid == GLOBALTABLESPACE_OID)
        relation->rd_locator.dbOid = InvalidOid;
    else
        relation->rd_locator.dbOid = MyDatabaseId;
 
    if (relation->rd_rel->relfilenode)
    {
        /*
         * Even if we are using a decoding snapshot that doesn't represent the
         * current state of the catalog we need to make sure the filenode
         * points to the current file since the older file will be gone (or
         * truncated). The new file will still contain older rows so lookups
         * in them will work correctly. This wouldn't work correctly if
         * rewrites were allowed to change the schema in an incompatible way,
         * but those are prevented both on catalog tables and on user tables
         * declared as additional catalog tables.
         */
        if (HistoricSnapshotActive()
            && RelationIsAccessibleInLogicalDecoding(relation)
            && IsTransactionState())
        {
            HeapTuple   phys_tuple;
            Form_pg_class physrel;
 
            phys_tuple = ScanPgRelation(RelationGetRelid(relation),
                                        RelationGetRelid(relation) != ClassOidIndexId,
                                        true);
            if (!HeapTupleIsValid(phys_tuple))
                elog(ERROR, "could not find pg_class entry for %u",
                     RelationGetRelid(relation));
            physrel = (Form_pg_class) GETSTRUCT(phys_tuple);
 
            relation->rd_rel->reltablespace = physrel->reltablespace;
            relation->rd_rel->relfilenode = physrel->relfilenode;
            heap_freetuple(phys_tuple);
        }
 
        relation->rd_locator.relNumber = relation->rd_rel->relfilenode;
    }
    else
    {
        /* Consult the relation mapper */
        relation->rd_locator.relNumber =
            RelationMapOidToFilenumber(relation->rd_id,
                                       relation->rd_rel->relisshared);
        if (!RelFileNumberIsValid(relation->rd_locator.relNumber))
            elog(ERROR, "could not find relation mapping for relation \"%s\", OID %u",
                 RelationGetRelationName(relation), relation->rd_id);
    }
 
    /*
     * For RelationNeedsWAL() to answer correctly on parallel workers, restore
     * rd_firstRelfilelocatorSubid.  No subtransactions start or end while in
     * parallel mode, so the specific SubTransactionId does not matter.
     */
    if (IsParallelWorker() && oldnumber != relation->rd_locator.relNumber)
    {
        if (RelFileLocatorSkippingWAL(relation->rd_locator))
            relation->rd_firstRelfilelocatorSubid = TopSubTransactionId;
        else
            relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    }
}
 
/*
 * Fill in the IndexAmRoutine for an index relation.
 *
 * relation's rd_amhandler and rd_indexcxt must be valid already.
 */
static void
InitIndexAmRoutine(Relation relation)
{
    IndexAmRoutine *cached,
               *tmp;
 
    /*
     * Call the amhandler in current, short-lived memory context, just in case
     * it leaks anything (it probably won't, but let's be paranoid).
     */
    tmp = GetIndexAmRoutine(relation->rd_amhandler);
 
    /* OK, now transfer the data into relation's rd_indexcxt. */
    cached = (IndexAmRoutine *) MemoryContextAlloc(relation->rd_indexcxt,
                                                   sizeof(IndexAmRoutine));
    memcpy(cached, tmp, sizeof(IndexAmRoutine));
    relation->rd_indam = cached;
 
    pfree(tmp);
}
 
/*
 * Initialize index-access-method support data for an index relation
 */
void
RelationInitIndexAccessInfo(Relation relation)
{
    HeapTuple   tuple;
    Form_pg_am  aform;
    Datum       indcollDatum;
    Datum       indclassDatum;
    Datum       indoptionDatum;
    bool        isnull;
    oidvector  *indcoll;
    oidvector  *indclass;
    int2vector *indoption;
    MemoryContext indexcxt;
    MemoryContext oldcontext;
    int         indnatts;
    int         indnkeyatts;
    uint16      amsupport;
 
    /*
     * Make a copy of the pg_index entry for the index.  Since pg_index
     * contains variable-length and possibly-null fields, we have to do this
     * honestly rather than just treating it as a Form_pg_index struct.
     */
    tuple = SearchSysCache1(INDEXRELID,
                            ObjectIdGetDatum(RelationGetRelid(relation)));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for index %u",
             RelationGetRelid(relation));
    oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
    relation->rd_indextuple = heap_copytuple(tuple);
    relation->rd_index = (Form_pg_index) GETSTRUCT(relation->rd_indextuple);
    MemoryContextSwitchTo(oldcontext);
    ReleaseSysCache(tuple);
 
    /*
     * Look up the index's access method, save the OID of its handler function
     */
    Assert(relation->rd_rel->relam != InvalidOid);
    tuple = SearchSysCache1(AMOID, ObjectIdGetDatum(relation->rd_rel->relam));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for access method %u",
             relation->rd_rel->relam);
    aform = (Form_pg_am) GETSTRUCT(tuple);
    relation->rd_amhandler = aform->amhandler;
    ReleaseSysCache(tuple);
 
    indnatts = RelationGetNumberOfAttributes(relation);
    if (indnatts != IndexRelationGetNumberOfAttributes(relation))
        elog(ERROR, "relnatts disagrees with indnatts for index %u",
             RelationGetRelid(relation));
    indnkeyatts = IndexRelationGetNumberOfKeyAttributes(relation);
 
    /*
     * Make the private context to hold index access info.  The reason we need
     * a context, and not just a couple of pallocs, is so that we won't leak
     * any subsidiary info attached to fmgr lookup records.
     */
    indexcxt = AllocSetContextCreate(CacheMemoryContext,
                                     "index info",
                                     ALLOCSET_SMALL_SIZES);
    relation->rd_indexcxt = indexcxt;
    MemoryContextCopyAndSetIdentifier(indexcxt,
                                      RelationGetRelationName(relation));
 
    /*
     * Now we can fetch the index AM's API struct
     */
    InitIndexAmRoutine(relation);
 
    /*
     * Allocate arrays to hold data. Opclasses are not used for included
     * columns, so allocate them for indnkeyatts only.
     */
    relation->rd_opfamily = (Oid *)
        MemoryContextAllocZero(indexcxt, indnkeyatts * sizeof(Oid));
    relation->rd_opcintype = (Oid *)
        MemoryContextAllocZero(indexcxt, indnkeyatts * sizeof(Oid));
 
    amsupport = relation->rd_indam->amsupport;
    if (amsupport > 0)
    {
        int         nsupport = indnatts * amsupport;
 
        relation->rd_support = (RegProcedure *)
            MemoryContextAllocZero(indexcxt, nsupport * sizeof(RegProcedure));
        relation->rd_supportinfo = (FmgrInfo *)
            MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
    }
    else
    {
        relation->rd_support = NULL;
        relation->rd_supportinfo = NULL;
    }
 
    relation->rd_indcollation = (Oid *)
        MemoryContextAllocZero(indexcxt, indnkeyatts * sizeof(Oid));
 
    relation->rd_indoption = (int16 *)
        MemoryContextAllocZero(indexcxt, indnkeyatts * sizeof(int16));
 
    /*
     * indcollation cannot be referenced directly through the C struct,
     * because it comes after the variable-width indkey field.  Must extract
     * the datum the hard way...
     */
    indcollDatum = fastgetattr(relation->rd_indextuple,
                               Anum_pg_index_indcollation,
                               GetPgIndexDescriptor(),
                               &isnull);
    Assert(!isnull);
    indcoll = (oidvector *) DatumGetPointer(indcollDatum);
    memcpy(relation->rd_indcollation, indcoll->values, indnkeyatts * sizeof(Oid));
 
    /*
     * indclass cannot be referenced directly through the C struct, because it
     * comes after the variable-width indkey field.  Must extract the datum
     * the hard way...
     */
    indclassDatum = fastgetattr(relation->rd_indextuple,
                                Anum_pg_index_indclass,
                                GetPgIndexDescriptor(),
                                &isnull);
    Assert(!isnull);
    indclass = (oidvector *) DatumGetPointer(indclassDatum);
 
    /*
     * Fill the support procedure OID array, as well as the info about
     * opfamilies and opclass input types.  (aminfo and supportinfo are left
     * as zeroes, and are filled on-the-fly when used)
     */
    IndexSupportInitialize(indclass, relation->rd_support,
                           relation->rd_opfamily, relation->rd_opcintype,
                           amsupport, indnkeyatts);
 
    /*
     * Similarly extract indoption and copy it to the cache entry
     */
    indoptionDatum = fastgetattr(relation->rd_indextuple,
                                 Anum_pg_index_indoption,
                                 GetPgIndexDescriptor(),
                                 &isnull);
    Assert(!isnull);
    indoption = (int2vector *) DatumGetPointer(indoptionDatum);
    memcpy(relation->rd_indoption, indoption->values, indnkeyatts * sizeof(int16));
 
    (void) RelationGetIndexAttOptions(relation, false);
 
    /*
     * expressions, predicate, exclusion caches will be filled later
     */
    relation->rd_indexprs = NIL;
    relation->rd_indpred = NIL;
    relation->rd_exclops = NULL;
    relation->rd_exclprocs = NULL;
    relation->rd_exclstrats = NULL;
    relation->rd_amcache = NULL;
}
 
/*
 * IndexSupportInitialize
 *      Initializes an index's cached opclass information,
 *      given the index's pg_index.indclass entry.
 *
 * Data is returned into *indexSupport, *opFamily, and *opcInType,
 * which are arrays allocated by the caller.
 *
 * The caller also passes maxSupportNumber and maxAttributeNumber, since these
 * indicate the size of the arrays it has allocated --- but in practice these
 * numbers must always match those obtainable from the system catalog entries
 * for the index and access method.
 */
static void
IndexSupportInitialize(oidvector *indclass,
                       RegProcedure *indexSupport,
                       Oid *opFamily,
                       Oid *opcInType,
                       StrategyNumber maxSupportNumber,
                       AttrNumber maxAttributeNumber)
{
    int         attIndex;
 
    for (attIndex = 0; attIndex < maxAttributeNumber; attIndex++)
    {
        OpClassCacheEnt *opcentry;
 
        if (!OidIsValid(indclass->values[attIndex]))
            elog(ERROR, "bogus pg_index tuple");
 
        /* look up the info for this opclass, using a cache */
        opcentry = LookupOpclassInfo(indclass->values[attIndex],
                                     maxSupportNumber);
 
        /* copy cached data into relcache entry */
        opFamily[attIndex] = opcentry->opcfamily;
        opcInType[attIndex] = opcentry->opcintype;
        if (maxSupportNumber > 0)
            memcpy(&indexSupport[attIndex * maxSupportNumber],
                   opcentry->supportProcs,
                   maxSupportNumber * sizeof(RegProcedure));
    }
}
 
/*
 * LookupOpclassInfo
 *
 * This routine maintains a per-opclass cache of the information needed
 * by IndexSupportInitialize().  This is more efficient than relying on
 * the catalog cache, because we can load all the info about a particular
 * opclass in a single indexscan of pg_amproc.
 *
 * The information from pg_am about expected range of support function
 * numbers is passed in, rather than being looked up, mainly because the
 * caller will have it already.
 *
 * Note there is no provision for flushing the cache.  This is OK at the
 * moment because there is no way to ALTER any interesting properties of an
 * existing opclass --- all you can do is drop it, which will result in
 * a useless but harmless dead entry in the cache.  To support altering
 * opclass membership (not the same as opfamily membership!), we'd need to
 * be able to flush this cache as well as the contents of relcache entries
 * for indexes.
 */
static OpClassCacheEnt *
LookupOpclassInfo(Oid operatorClassOid,
                  StrategyNumber numSupport)
{
    OpClassCacheEnt *opcentry;
    bool        found;
    Relation    rel;
    SysScanDesc scan;
    ScanKeyData skey[3];
    HeapTuple   htup;
    bool        indexOK;
 
    if (OpClassCache == NULL)
    {
        /* First time through: initialize the opclass cache */
        HASHCTL     ctl;
 
        /* Also make sure CacheMemoryContext exists */
        if (!CacheMemoryContext)
            CreateCacheMemoryContext();
 
        ctl.keysize = sizeof(Oid);
        ctl.entrysize = sizeof(OpClassCacheEnt);
        OpClassCache = hash_create("Operator class cache", 64,
                                   &ctl, HASH_ELEM | HASH_BLOBS);
    }
 
    opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
                                               &operatorClassOid,
                                               HASH_ENTER, &found);
 
    if (!found)
    {
        /* Initialize new entry */
        opcentry->valid = false;    /* until known OK */
        opcentry->numSupport = numSupport;
        opcentry->supportProcs = NULL;  /* filled below */
    }
    else
    {
        Assert(numSupport == opcentry->numSupport);
    }
 
    /*
     * When aggressively testing cache-flush hazards, we disable the operator
     * class cache and force reloading of the info on each call.  This models
     * no real-world behavior, since the cache entries are never invalidated
     * otherwise.  However it can be helpful for detecting bugs in the cache
     * loading logic itself, such as reliance on a non-nailed index.  Given
     * the limited use-case and the fact that this adds a great deal of
     * expense, we enable it only for high values of debug_discard_caches.
     */
#ifdef DISCARD_CACHES_ENABLED
    if (debug_discard_caches > 2)
        opcentry->valid = false;
#endif
 
    if (opcentry->valid)
        return opcentry;
 
    /*
     * Need to fill in new entry.  First allocate space, unless we already did
     * so in some previous attempt.
     */
    if (opcentry->supportProcs == NULL && numSupport > 0)
        opcentry->supportProcs = (RegProcedure *)
            MemoryContextAllocZero(CacheMemoryContext,
                                   numSupport * sizeof(RegProcedure));
 
    /*
     * To avoid infinite recursion during startup, force heap scans if we're
     * looking up info for the opclasses used by the indexes we would like to
     * reference here.
     */
    indexOK = criticalRelcachesBuilt ||
        (operatorClassOid != OID_BTREE_OPS_OID &&
         operatorClassOid != INT2_BTREE_OPS_OID);
 
    /*
     * We have to fetch the pg_opclass row to determine its opfamily and
     * opcintype, which are needed to look up related operators and functions.
     * It'd be convenient to use the syscache here, but that probably doesn't
     * work while bootstrapping.
     */
    ScanKeyInit(&skey[0],
                Anum_pg_opclass_oid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(operatorClassOid));
    rel = table_open(OperatorClassRelationId, AccessShareLock);
    scan = systable_beginscan(rel, OpclassOidIndexId, indexOK,
                              NULL, 1, skey);
 
    if (HeapTupleIsValid(htup = systable_getnext(scan)))
    {
        Form_pg_opclass opclassform = (Form_pg_opclass) GETSTRUCT(htup);
 
        opcentry->opcfamily = opclassform->opcfamily;
        opcentry->opcintype = opclassform->opcintype;
    }
    else
        elog(ERROR, "could not find tuple for opclass %u", operatorClassOid);
 
    systable_endscan(scan);
    table_close(rel, AccessShareLock);
 
    /*
     * Scan pg_amproc to obtain support procs for the opclass.  We only fetch
     * the default ones (those with lefttype = righttype = opcintype).
     */
    if (numSupport > 0)
    {
        ScanKeyInit(&skey[0],
                    Anum_pg_amproc_amprocfamily,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcfamily));
        ScanKeyInit(&skey[1],
                    Anum_pg_amproc_amproclefttype,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcintype));
        ScanKeyInit(&skey[2],
                    Anum_pg_amproc_amprocrighttype,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcintype));
        rel = table_open(AccessMethodProcedureRelationId, AccessShareLock);
        scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
                                  NULL, 3, skey);
 
        while (HeapTupleIsValid(htup = systable_getnext(scan)))
        {
            Form_pg_amproc amprocform = (Form_pg_amproc) GETSTRUCT(htup);
 
            if (amprocform->amprocnum <= 0 ||
                (StrategyNumber) amprocform->amprocnum > numSupport)
                elog(ERROR, "invalid amproc number %d for opclass %u",
                     amprocform->amprocnum, operatorClassOid);
 
            opcentry->supportProcs[amprocform->amprocnum - 1] =
                amprocform->amproc;
        }
 
        systable_endscan(scan);
        table_close(rel, AccessShareLock);
    }
 
    opcentry->valid = true;
    return opcentry;
}
 
/*
 * Fill in the TableAmRoutine for a relation
 *
 * relation's rd_amhandler must be valid already.
 */
static void
InitTableAmRoutine(Relation relation)
{
    relation->rd_tableam = GetTableAmRoutine(relation->rd_amhandler);
}
 
/*
 * Initialize table access method support for a table like relation
 */
void
RelationInitTableAccessMethod(Relation relation)
{
    HeapTuple   tuple;
    Form_pg_am  aform;
 
    if (relation->rd_rel->relkind == RELKIND_SEQUENCE)
    {
        /*
         * Sequences are currently accessed like heap tables, but it doesn't
         * seem prudent to show that in the catalog. So just overwrite it
         * here.
         */
        Assert(relation->rd_rel->relam == InvalidOid);
        relation->rd_amhandler = F_HEAP_TABLEAM_HANDLER;
    }
    else if (IsCatalogRelation(relation))
    {
        /*
         * Avoid doing a syscache lookup for catalog tables.
         */
        Assert(relation->rd_rel->relam == HEAP_TABLE_AM_OID);
        relation->rd_amhandler = F_HEAP_TABLEAM_HANDLER;
    }
    else
    {
        /*
         * Look up the table access method, save the OID of its handler
         * function.
         */
        Assert(relation->rd_rel->relam != InvalidOid);
        tuple = SearchSysCache1(AMOID,
                                ObjectIdGetDatum(relation->rd_rel->relam));
        if (!HeapTupleIsValid(tuple))
            elog(ERROR, "cache lookup failed for access method %u",
                 relation->rd_rel->relam);
        aform = (Form_pg_am) GETSTRUCT(tuple);
        relation->rd_amhandler = aform->amhandler;
        ReleaseSysCache(tuple);
    }
 
    /*
     * Now we can fetch the table AM's API struct
     */
    InitTableAmRoutine(relation);
}
 
/*
 *      formrdesc
 *
 *      This is a special cut-down version of RelationBuildDesc(),
 *      used while initializing the relcache.
 *      The relation descriptor is built just from the supplied parameters,
 *      without actually looking at any system table entries.  We cheat
 *      quite a lot since we only need to work for a few basic system
 *      catalogs.
 *
 * The catalogs this is used for can't have constraints (except attnotnull),
 * default values, rules, or triggers, since we don't cope with any of that.
 * (Well, actually, this only matters for properties that need to be valid
 * during bootstrap or before RelationCacheInitializePhase3 runs, and none of
 * these properties matter then...)
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static void
formrdesc(const char *relationName, Oid relationReltype,
          bool isshared,
          int natts, const FormData_pg_attribute *attrs)
{
    Relation    relation;
    int         i;
    bool        has_not_null;
 
    /*
     * allocate new relation desc, clear all fields of reldesc
     */
    relation = (Relation) palloc0(sizeof(RelationData));
 
    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;
 
    /*
     * initialize reference count: 1 because it is nailed in cache
     */
    relation->rd_refcnt = 1;
 
    /*
     * all entries built with this routine are nailed-in-cache; none are for
     * new or temp relations.
     */
    relation->rd_isnailed = true;
    relation->rd_createSubid = InvalidSubTransactionId;
    relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_droppedSubid = InvalidSubTransactionId;
    relation->rd_backend = INVALID_PROC_NUMBER;
    relation->rd_islocaltemp = false;
 
    /*
     * initialize relation tuple form
     *
     * The data we insert here is pretty incomplete/bogus, but it'll serve to
     * get us launched.  RelationCacheInitializePhase3() will read the real
     * data from pg_class and replace what we've done here.  Note in
     * particular that relowner is left as zero; this cues
     * RelationCacheInitializePhase3 that the real data isn't there yet.
     */
    relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);
 
    namestrcpy(&relation->rd_rel->relname, relationName);
    relation->rd_rel->relnamespace = PG_CATALOG_NAMESPACE;
    relation->rd_rel->reltype = relationReltype;
 
    /*
     * It's important to distinguish between shared and non-shared relations,
     * even at bootstrap time, to make sure we know where they are stored.
     */
    relation->rd_rel->relisshared = isshared;
    if (isshared)
        relation->rd_rel->reltablespace = GLOBALTABLESPACE_OID;
 
    /* formrdesc is used only for permanent relations */
    relation->rd_rel->relpersistence = RELPERSISTENCE_PERMANENT;
 
    /* ... and they're always populated, too */
    relation->rd_rel->relispopulated = true;
 
    relation->rd_rel->relreplident = REPLICA_IDENTITY_NOTHING;
    relation->rd_rel->relpages = 0;
    relation->rd_rel->reltuples = -1;
    relation->rd_rel->relallvisible = 0;
    relation->rd_rel->relkind = RELKIND_RELATION;
    relation->rd_rel->relnatts = (int16) natts;
 
    /*
     * initialize attribute tuple form
     *
     * Unlike the case with the relation tuple, this data had better be right
     * because it will never be replaced.  The data comes from
     * src/include/catalog/ headers via genbki.pl.
     */
    relation->rd_att = CreateTemplateTupleDesc(natts);
    relation->rd_att->tdrefcount = 1;   /* mark as refcounted */
 
    relation->rd_att->tdtypeid = relationReltype;
    relation->rd_att->tdtypmod = -1;    /* just to be sure */
 
    /*
     * initialize tuple desc info
     */
    has_not_null = false;
    for (i = 0; i < natts; i++)
    {
        memcpy(TupleDescAttr(relation->rd_att, i),
               &attrs[i],
               ATTRIBUTE_FIXED_PART_SIZE);
        has_not_null |= attrs[i].attnotnull;
 
        populate_compact_attribute(relation->rd_att, i);
    }
 
    /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
    TupleDescCompactAttr(relation->rd_att, 0)->attcacheoff = 0;
 
    /* mark not-null status */
    if (has_not_null)
    {
        TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));
 
        constr->has_not_null = true;
        relation->rd_att->constr = constr;
    }
 
    /*
     * initialize relation id from info in att array (my, this is ugly)
     */
    RelationGetRelid(relation) = TupleDescAttr(relation->rd_att, 0)->attrelid;
 
    /*
     * All relations made with formrdesc are mapped.  This is necessarily so
     * because there is no other way to know what filenumber they currently
     * have.  In bootstrap mode, add them to the initial relation mapper data,
     * specifying that the initial filenumber is the same as the OID.
     */
    relation->rd_rel->relfilenode = InvalidRelFileNumber;
    if (IsBootstrapProcessingMode())
        RelationMapUpdateMap(RelationGetRelid(relation),
                             RelationGetRelid(relation),
                             isshared, true);
 
    /*
     * initialize the relation lock manager information
     */
    RelationInitLockInfo(relation); /* see lmgr.c */
 
    /*
     * initialize physical addressing information for the relation
     */
    RelationInitPhysicalAddr(relation);
 
    /*
     * initialize the table am handler
     */
    relation->rd_rel->relam = HEAP_TABLE_AM_OID;
    relation->rd_tableam = GetHeapamTableAmRoutine();
 
    /*
     * initialize the rel-has-index flag, using hardwired knowledge
     */
    if (IsBootstrapProcessingMode())
    {
        /* In bootstrap mode, we have no indexes */
        relation->rd_rel->relhasindex = false;
    }
    else
    {
        /* Otherwise, all the rels formrdesc is used for have indexes */
        relation->rd_rel->relhasindex = true;
    }
 
    /*
     * add new reldesc to relcache
     */
    RelationCacheInsert(relation, false);
 
    /* It's fully valid */
    relation->rd_isvalid = true;
}
 
 
/* ----------------------------------------------------------------
 *               Relation Descriptor Lookup Interface
 * ----------------------------------------------------------------
 */
 
/*
 *      RelationIdGetRelation
 *
 *      Lookup a reldesc by OID; make one if not already in cache.
 *
 *      Returns NULL if no pg_class row could be found for the given relid
 *      (suggesting we are trying to access a just-deleted relation).
 *      Any other error is reported via elog.
 *
 *      NB: caller should already have at least AccessShareLock on the
 *      relation ID, else there are nasty race conditions.
 *
 *      NB: relation ref count is incremented, or set to 1 if new entry.
 *      Caller should eventually decrement count.  (Usually,
 *      that happens by calling RelationClose().)
 */
Relation
RelationIdGetRelation(Oid relationId)
{
    Relation    rd;
 
    /* Make sure we're in an xact, even if this ends up being a cache hit */
    Assert(IsTransactionState());
 
    /*
     * first try to find reldesc in the cache
     */
    RelationIdCacheLookup(relationId, rd);
 
    if (RelationIsValid(rd))
    {
        /* return NULL for dropped relations */
        if (rd->rd_droppedSubid != InvalidSubTransactionId)
        {
            Assert(!rd->rd_isvalid);
            return NULL;
        }
 
        RelationIncrementReferenceCount(rd);
        /* revalidate cache entry if necessary */
        if (!rd->rd_isvalid)
        {
            RelationRebuildRelation(rd);
 
            /*
             * Normally entries need to be valid here, but before the relcache
             * has been initialized, not enough infrastructure exists to
             * perform pg_class lookups. The structure of such entries doesn't
             * change, but we still want to update the rd_rel entry. So
             * rd_isvalid = false is left in place for a later lookup.
             */
            Assert(rd->rd_isvalid ||
                   (rd->rd_isnailed && !criticalRelcachesBuilt));
        }
        return rd;
    }
 
    /*
     * no reldesc in the cache, so have RelationBuildDesc() build one and add
     * it.
     */
    rd = RelationBuildDesc(relationId, true);
    if (RelationIsValid(rd))
        RelationIncrementReferenceCount(rd);
    return rd;
}
 
/* ----------------------------------------------------------------
 *              cache invalidation support routines
 * ----------------------------------------------------------------
 */
 
/* ResourceOwner callbacks to track relcache references */
static void ResOwnerReleaseRelation(Datum res);
static char *ResOwnerPrintRelCache(Datum res);
 
static const ResourceOwnerDesc relref_resowner_desc =
{
    .name = "relcache reference",
    .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
    .release_priority = RELEASE_PRIO_RELCACHE_REFS,
    .ReleaseResource = ResOwnerReleaseRelation,
    .DebugPrint = ResOwnerPrintRelCache
};
 
/* Convenience wrappers over ResourceOwnerRemember/Forget */
static inline void
ResourceOwnerRememberRelationRef(ResourceOwner owner, Relation rel)
{
    ResourceOwnerRemember(owner, PointerGetDatum(rel), &relref_resowner_desc);
}
static inline void
ResourceOwnerForgetRelationRef(ResourceOwner owner, Relation rel)
{
    ResourceOwnerForget(owner, PointerGetDatum(rel), &relref_resowner_desc);
}
 
/*
 * RelationIncrementReferenceCount
 *      Increments relation reference count.
 *
 * Note: bootstrap mode has its own weird ideas about relation refcount
 * behavior; we ought to fix it someday, but for now, just disable
 * reference count ownership tracking in bootstrap mode.
 */
void
RelationIncrementReferenceCount(Relation rel)
{
    ResourceOwnerEnlarge(CurrentResourceOwner);
    rel->rd_refcnt += 1;
    if (!IsBootstrapProcessingMode())
        ResourceOwnerRememberRelationRef(CurrentResourceOwner, rel);
}
 
/*
 * RelationDecrementReferenceCount
 *      Decrements relation reference count.
 */
void
RelationDecrementReferenceCount(Relation rel)
{
    Assert(rel->rd_refcnt > 0);
    rel->rd_refcnt -= 1;
    if (!IsBootstrapProcessingMode())
        ResourceOwnerForgetRelationRef(CurrentResourceOwner, rel);
}
 
/*
 * RelationClose - close an open relation
 *
 *  Actually, we just decrement the refcount.
 *
 *  NOTE: if compiled with -DRELCACHE_FORCE_RELEASE then relcache entries
 *  will be freed as soon as their refcount goes to zero.  In combination
 *  with aset.c's CLOBBER_FREED_MEMORY option, this provides a good test
 *  to catch references to already-released relcache entries.  It slows
 *  things down quite a bit, however.
 */
void
RelationClose(Relation relation)
{
    /* Note: no locking manipulations needed */
    RelationDecrementReferenceCount(relation);
 
    RelationCloseCleanup(relation);
}
 
static void
RelationCloseCleanup(Relation relation)
{
    /*
     * If the relation is no longer open in this session, we can clean up any
     * stale partition descriptors it has.  This is unlikely, so check to see
     * if there are child contexts before expending a call to mcxt.c.
     */
    if (RelationHasReferenceCountZero(relation))
    {
        if (relation->rd_pdcxt != NULL &&
            relation->rd_pdcxt->firstchild != NULL)
            MemoryContextDeleteChildren(relation->rd_pdcxt);
 
        if (relation->rd_pddcxt != NULL &&
            relation->rd_pddcxt->firstchild != NULL)
            MemoryContextDeleteChildren(relation->rd_pddcxt);
    }
 
#ifdef RELCACHE_FORCE_RELEASE
    if (RelationHasReferenceCountZero(relation) &&
        relation->rd_createSubid == InvalidSubTransactionId &&
        relation->rd_firstRelfilelocatorSubid == InvalidSubTransactionId)
        RelationClearRelation(relation);
#endif
}
 
/*
 * RelationReloadIndexInfo - reload minimal information for an open index
 *
 *  This function is used only for indexes.  A relcache inval on an index
 *  can mean that its pg_class or pg_index row changed.  There are only
 *  very limited changes that are allowed to an existing index's schema,
 *  so we can update the relcache entry without a complete rebuild; which
 *  is fortunate because we can't rebuild an index entry that is "nailed"
 *  and/or in active use.  We support full replacement of the pg_class row,
 *  as well as updates of a few simple fields of the pg_index row.
 *
 *  We assume that at the time we are called, we have at least AccessShareLock
 *  on the target index.
 *
 *  If the target index is an index on pg_class or pg_index, we'd better have
 *  previously gotten at least AccessShareLock on its underlying catalog,
 *  else we are at risk of deadlock against someone trying to exclusive-lock
 *  the heap and index in that order.  This is ensured in current usage by
 *  only applying this to indexes being opened or having positive refcount.
 */
static void
RelationReloadIndexInfo(Relation relation)
{
    bool        indexOK;
    HeapTuple   pg_class_tuple;
    Form_pg_class relp;
 
    /* Should be called only for invalidated, live indexes */
    Assert((relation->rd_rel->relkind == RELKIND_INDEX ||
            relation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX) &&
           !relation->rd_isvalid &&
           relation->rd_droppedSubid == InvalidSubTransactionId);
 
    /*
     * If it's a shared index, we might be called before backend startup has
     * finished selecting a database, in which case we have no way to read
     * pg_class yet.  However, a shared index can never have any significant
     * schema updates, so it's okay to mostly ignore the invalidation signal.
     * Its physical relfilenumber might've changed, but that's all.  Update
     * the physical relfilenumber, mark it valid and return without doing
     * anything more.
     */
    if (relation->rd_rel->relisshared && !criticalRelcachesBuilt)
    {
        RelationInitPhysicalAddr(relation);
        relation->rd_isvalid = true;
        return;
    }
 
    /*
     * Read the pg_class row
     *
     * Don't try to use an indexscan of pg_class_oid_index to reload the info
     * for pg_class_oid_index ...
     */
    indexOK = (RelationGetRelid(relation) != ClassOidIndexId);
    pg_class_tuple = ScanPgRelation(RelationGetRelid(relation), indexOK, false);
    if (!HeapTupleIsValid(pg_class_tuple))
        elog(ERROR, "could not find pg_class tuple for index %u",
             RelationGetRelid(relation));
    relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
    memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
    /* Reload reloptions in case they changed */
    if (relation->rd_options)
        pfree(relation->rd_options);
    RelationParseRelOptions(relation, pg_class_tuple);
    /* done with pg_class tuple */
    heap_freetuple(pg_class_tuple);
    /* We must recalculate physical address in case it changed */
    RelationInitPhysicalAddr(relation);
 
    /*
     * For a non-system index, there are fields of the pg_index row that are
     * allowed to change, so re-read that row and update the relcache entry.
     * Most of the info derived from pg_index (such as support function lookup
     * info) cannot change, and indeed the whole point of this routine is to
     * update the relcache entry without clobbering that data; so wholesale
     * replacement is not appropriate.
     */
    if (!IsSystemRelation(relation))
    {
        HeapTuple   tuple;
        Form_pg_index index;
 
        tuple = SearchSysCache1(INDEXRELID,
                                ObjectIdGetDatum(RelationGetRelid(relation)));
        if (!HeapTupleIsValid(tuple))
            elog(ERROR, "cache lookup failed for index %u",
                 RelationGetRelid(relation));
        index = (Form_pg_index) GETSTRUCT(tuple);
 
        /*
         * Basically, let's just copy all the bool fields.  There are one or
         * two of these that can't actually change in the current code, but
         * it's not worth it to track exactly which ones they are.  None of
         * the array fields are allowed to change, though.
         */
        relation->rd_index->indisunique = index->indisunique;
        relation->rd_index->indnullsnotdistinct = index->indnullsnotdistinct;
        relation->rd_index->indisprimary = index->indisprimary;
        relation->rd_index->indisexclusion = index->indisexclusion;
        relation->rd_index->indimmediate = index->indimmediate;
        relation->rd_index->indisclustered = index->indisclustered;
        relation->rd_index->indisvalid = index->indisvalid;
        relation->rd_index->indcheckxmin = index->indcheckxmin;
        relation->rd_index->indisready = index->indisready;
        relation->rd_index->indislive = index->indislive;
        relation->rd_index->indisreplident = index->indisreplident;
 
        /* Copy xmin too, as that is needed to make sense of indcheckxmin */
        HeapTupleHeaderSetXmin(relation->rd_indextuple->t_data,
                               HeapTupleHeaderGetXmin(tuple->t_data));
 
        ReleaseSysCache(tuple);
    }
 
    /* Okay, now it's valid again */
    relation->rd_isvalid = true;
}
 
/*
 * RelationReloadNailed - reload minimal information for nailed relations.
 *
 * The structure of a nailed relation can never change (which is good, because
 * we rely on knowing their structure to be able to read catalog content). But
 * some parts, e.g. pg_class.relfrozenxid, are still important to have
 * accurate content for. Therefore those need to be reloaded after the arrival
 * of invalidations.
 */
static void
RelationReloadNailed(Relation relation)
{
    /* Should be called only for invalidated, nailed relations */
    Assert(!relation->rd_isvalid);
    Assert(relation->rd_isnailed);
    /* nailed indexes are handled by RelationReloadIndexInfo() */
    Assert(relation->rd_rel->relkind == RELKIND_RELATION);
    /* can only reread catalog contents in a transaction */
    Assert(IsTransactionState());
 
    /*
     * Redo RelationInitPhysicalAddr in case it is a mapped relation whose
     * mapping changed.
     */
    RelationInitPhysicalAddr(relation);
 
    /*
     * Reload a non-index entry.  We can't easily do so if relcaches aren't
     * yet built, but that's fine because at that stage the attributes that
     * need to be current (like relfrozenxid) aren't yet accessed.  To ensure
     * the entry will later be revalidated, we leave it in invalid state, but
     * allow use (cf. RelationIdGetRelation()).
     */
    if (criticalRelcachesBuilt)
    {
        HeapTuple   pg_class_tuple;
        Form_pg_class relp;
 
        /*
         * NB: Mark the entry as valid before starting to scan, to avoid
         * self-recursion when re-building pg_class.
         */
        relation->rd_isvalid = true;
 
        pg_class_tuple = ScanPgRelation(RelationGetRelid(relation),
                                        true, false);
        relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
        memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
        heap_freetuple(pg_class_tuple);
 
        /*
         * Again mark as valid, to protect against concurrently arriving
         * invalidations.
         */
        relation->rd_isvalid = true;
    }
}
 
/*
 * RelationDestroyRelation
 *
 *  Physically delete a relation cache entry and all subsidiary data.
 *  Caller must already have unhooked the entry from the hash table.
 */
static void
RelationDestroyRelation(Relation relation, bool remember_tupdesc)
{
    Assert(RelationHasReferenceCountZero(relation));
 
    /*
     * Make sure smgr and lower levels close the relation's files, if they
     * weren't closed already.  (This was probably done by caller, but let's
     * just be real sure.)
     */
    RelationCloseSmgr(relation);
 
    /* break mutual link with stats entry */
    pgstat_unlink_relation(relation);
 
    /*
     * Free all the subsidiary data structures of the relcache entry, then the
     * entry itself.
     */
    if (relation->rd_rel)
        pfree(relation->rd_rel);
    /* can't use DecrTupleDescRefCount here */
    Assert(relation->rd_att->tdrefcount > 0);
    if (--relation->rd_att->tdrefcount == 0)
    {
        /*
         * If we Rebuilt a relcache entry during a transaction then its
         * possible we did that because the TupDesc changed as the result of
         * an ALTER TABLE that ran at less than AccessExclusiveLock. It's
         * possible someone copied that TupDesc, in which case the copy would
         * point to free'd memory. So if we rebuild an entry we keep the
         * TupDesc around until end of transaction, to be safe.
         */
        if (remember_tupdesc)
            RememberToFreeTupleDescAtEOX(relation->rd_att);
        else
            FreeTupleDesc(relation->rd_att);
    }
    FreeTriggerDesc(relation->trigdesc);
    list_free_deep(relation->rd_fkeylist);
    list_free(relation->rd_indexlist);
    list_free(relation->rd_statlist);
    bms_free(relation->rd_keyattr);
    bms_free(relation->rd_pkattr);
    bms_free(relation->rd_idattr);
    bms_free(relation->rd_hotblockingattr);
    bms_free(relation->rd_summarizedattr);
    if (relation->rd_pubdesc)
        pfree(relation->rd_pubdesc);
    if (relation->rd_options)
        pfree(relation->rd_options);
    if (relation->rd_indextuple)
        pfree(relation->rd_indextuple);
    if (relation->rd_amcache)
        pfree(relation->rd_amcache);
    if (relation->rd_fdwroutine)
        pfree(relation->rd_fdwroutine);
    if (relation->rd_indexcxt)
        MemoryContextDelete(relation->rd_indexcxt);
    if (relation->rd_rulescxt)
        MemoryContextDelete(relation->rd_rulescxt);
    if (relation->rd_rsdesc)
        MemoryContextDelete(relation->rd_rsdesc->rscxt);
    if (relation->rd_partkeycxt)
        MemoryContextDelete(relation->rd_partkeycxt);
    if (relation->rd_pdcxt)
        MemoryContextDelete(relation->rd_pdcxt);
    if (relation->rd_pddcxt)
        MemoryContextDelete(relation->rd_pddcxt);
    if (relation->rd_partcheckcxt)
        MemoryContextDelete(relation->rd_partcheckcxt);
    pfree(relation);
}
 
/*
 * RelationInvalidateRelation - mark a relation cache entry as invalid
 *
 * An entry that's marked as invalid will be reloaded on next access.
 */
static void
RelationInvalidateRelation(Relation relation)
{
    /*
     * Make sure smgr and lower levels close the relation's files, if they
     * weren't closed already.  If the relation is not getting deleted, the
     * next smgr access should reopen the files automatically.  This ensures
     * that the low-level file access state is updated after, say, a vacuum
     * truncation.
     */
    RelationCloseSmgr(relation);
 
    /* Free AM cached data, if any */
    if (relation->rd_amcache)
        pfree(relation->rd_amcache);
    relation->rd_amcache = NULL;
 
    relation->rd_isvalid = false;
}
 
/*
 * RelationClearRelation - physically blow away a relation cache entry
 *
 * The caller must ensure that the entry is no longer needed, i.e. its
 * reference count is zero.  Also, the rel or its storage must not be created
 * in the current transaction (rd_createSubid and rd_firstRelfilelocatorSubid
 * must not be set).
 */
static void
RelationClearRelation(Relation relation)
{
    Assert(RelationHasReferenceCountZero(relation));
    Assert(!relation->rd_isnailed);
 
    /*
     * Relations created in the same transaction must never be removed, see
     * RelationFlushRelation.
     */
    Assert(relation->rd_createSubid == InvalidSubTransactionId);
    Assert(relation->rd_firstRelfilelocatorSubid == InvalidSubTransactionId);
    Assert(relation->rd_droppedSubid == InvalidSubTransactionId);
 
    /* first mark it as invalid */
    RelationInvalidateRelation(relation);
 
    /* Remove it from the hash table */
    RelationCacheDelete(relation);
 
    /* And release storage */
    RelationDestroyRelation(relation, false);
}
 
/*
 * RelationRebuildRelation - rebuild a relation cache entry in place
 *
 * Reset and rebuild a relation cache entry from scratch (that is, from
 * catalog entries).  This is used when we are notified of a change to an open
 * relation (one with refcount > 0).  The entry is reconstructed without
 * moving the physical RelationData record, so that the refcount holder's
 * pointer is still valid.
 *
 * NB: when rebuilding, we'd better hold some lock on the relation, else the
 * catalog data we need to read could be changing under us.  Also, a rel to be
 * rebuilt had better have refcnt > 0.  This is because a sinval reset could
 * happen while we're accessing the catalogs, and the rel would get blown away
 * underneath us by RelationCacheInvalidate if it has zero refcnt.
 */
static void
RelationRebuildRelation(Relation relation)
{
    Assert(!RelationHasReferenceCountZero(relation));
    /* rebuilding requires access to the catalogs */
    Assert(IsTransactionState());
    /* there is no reason to ever rebuild a dropped relation */
    Assert(relation->rd_droppedSubid == InvalidSubTransactionId);
 
    /* Close and mark it as invalid until we've finished the rebuild */
    RelationInvalidateRelation(relation);
 
    /*
     * Indexes only have a limited number of possible schema changes, and we
     * don't want to use the full-blown procedure because it's a headache for
     * indexes that reload itself depends on.
     *
     * As an exception, use the full procedure if the index access info hasn't
     * been initialized yet.  Index creation relies on that: it first builds
     * the relcache entry with RelationBuildLocalRelation(), creates the
     * pg_index tuple only after that, and then relies on
     * CommandCounterIncrement to load the pg_index contents.
     */
    if ((relation->rd_rel->relkind == RELKIND_INDEX ||
         relation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX) &&
        relation->rd_indexcxt != NULL)
    {
        RelationReloadIndexInfo(relation);
        return;
    }
    /* Nailed relations are handled separately. */
    else if (relation->rd_isnailed)
    {
        RelationReloadNailed(relation);
        return;
    }
    else
    {
        /*
         * Our strategy for rebuilding an open relcache entry is to build a
         * new entry from scratch, swap its contents with the old entry, and
         * finally delete the new entry (along with any infrastructure swapped
         * over from the old entry).  This is to avoid trouble in case an
         * error causes us to lose control partway through.  The old entry
         * will still be marked !rd_isvalid, so we'll try to rebuild it again
         * on next access.  Meanwhile it's not any less valid than it was
         * before, so any code that might expect to continue accessing it
         * isn't hurt by the rebuild failure.  (Consider for example a
         * subtransaction that ALTERs a table and then gets canceled partway
         * through the cache entry rebuild.  The outer transaction should
         * still see the not-modified cache entry as valid.)  The worst
         * consequence of an error is leaking the necessarily-unreferenced new
         * entry, and this shouldn't happen often enough for that to be a big
         * problem.
         *
         * When rebuilding an open relcache entry, we must preserve ref count,
         * rd_*Subid, and rd_toastoid state.  Also attempt to preserve the
         * pg_class entry (rd_rel), tupledesc, rewrite-rule, partition key,
         * and partition descriptor substructures in place, because various
         * places assume that these structures won't move while they are
         * working with an open relcache entry.  (Note:  the refcount
         * mechanism for tupledescs might someday allow us to remove this hack
         * for the tupledesc.)
         *
         * Note that this process does not touch CurrentResourceOwner; which
         * is good because whatever ref counts the entry may have do not
         * necessarily belong to that resource owner.
         */
        Relation    newrel;
        Oid         save_relid = RelationGetRelid(relation);
        bool        keep_tupdesc;
        bool        keep_rules;
        bool        keep_policies;
        bool        keep_partkey;
 
        /* Build temporary entry, but don't link it into hashtable */
        newrel = RelationBuildDesc(save_relid, false);
 
        /*
         * Between here and the end of the swap, don't add code that does or
         * reasonably could read system catalogs.  That range must be free
         * from invalidation processing.  See RelationBuildDesc() manipulation
         * of in_progress_list.
         */
 
        if (newrel == NULL)
        {
            /*
             * We can validly get here, if we're using a historic snapshot in
             * which a relation, accessed from outside logical decoding, is
             * still invisible. In that case it's fine to just mark the
             * relation as invalid and return - it'll fully get reloaded by
             * the cache reset at the end of logical decoding (or at the next
             * access).  During normal processing we don't want to ignore this
             * case as it shouldn't happen there, as explained below.
             */
            if (HistoricSnapshotActive())
                return;
 
            /*
             * This shouldn't happen as dropping a relation is intended to be
             * impossible if still referenced (cf. CheckTableNotInUse()). But
             * if we get here anyway, we can't just delete the relcache entry,
             * as it possibly could get accessed later (as e.g. the error
             * might get trapped and handled via a subtransaction rollback).
             */
            elog(ERROR, "relation %u deleted while still in use", save_relid);
        }
 
        /*
         * If we were to, again, have cases of the relkind of a relcache entry
         * changing, we would need to ensure that pgstats does not get
         * confused.
         */
        Assert(relation->rd_rel->relkind == newrel->rd_rel->relkind);
 
        keep_tupdesc = equalTupleDescs(relation->rd_att, newrel->rd_att);
        keep_rules = equalRuleLocks(relation->rd_rules, newrel->rd_rules);
        keep_policies = equalRSDesc(relation->rd_rsdesc, newrel->rd_rsdesc);
        /* partkey is immutable once set up, so we can always keep it */
        keep_partkey = (relation->rd_partkey != NULL);
 
        /*
         * Perform swapping of the relcache entry contents.  Within this
         * process the old entry is momentarily invalid, so there *must* be no
         * possibility of CHECK_FOR_INTERRUPTS within this sequence. Do it in
         * all-in-line code for safety.
         *
         * Since the vast majority of fields should be swapped, our method is
         * to swap the whole structures and then re-swap those few fields we
         * didn't want swapped.
         */
#define SWAPFIELD(fldtype, fldname) \
        do { \
            fldtype _tmp = newrel->fldname; \
            newrel->fldname = relation->fldname; \
            relation->fldname = _tmp; \
        } while (0)
 
        /* swap all Relation struct fields */
        {
            RelationData tmpstruct;
 
            memcpy(&tmpstruct, newrel, sizeof(RelationData));
            memcpy(newrel, relation, sizeof(RelationData));
            memcpy(relation, &tmpstruct, sizeof(RelationData));
        }
 
        /* rd_smgr must not be swapped, due to back-links from smgr level */
        SWAPFIELD(SMgrRelation, rd_smgr);
        /* rd_refcnt must be preserved */
        SWAPFIELD(int, rd_refcnt);
        /* isnailed shouldn't change */
        Assert(newrel->rd_isnailed == relation->rd_isnailed);
        /* creation sub-XIDs must be preserved */
        SWAPFIELD(SubTransactionId, rd_createSubid);
        SWAPFIELD(SubTransactionId, rd_newRelfilelocatorSubid);
        SWAPFIELD(SubTransactionId, rd_firstRelfilelocatorSubid);
        SWAPFIELD(SubTransactionId, rd_droppedSubid);
        /* un-swap rd_rel pointers, swap contents instead */
        SWAPFIELD(Form_pg_class, rd_rel);
        /* ... but actually, we don't have to update newrel->rd_rel */
        memcpy(relation->rd_rel, newrel->rd_rel, CLASS_TUPLE_SIZE);
        /* preserve old tupledesc, rules, policies if no logical change */
        if (keep_tupdesc)
            SWAPFIELD(TupleDesc, rd_att);
        if (keep_rules)
        {
            SWAPFIELD(RuleLock *, rd_rules);
            SWAPFIELD(MemoryContext, rd_rulescxt);
        }
        if (keep_policies)
            SWAPFIELD(RowSecurityDesc *, rd_rsdesc);
        /* toast OID override must be preserved */
        SWAPFIELD(Oid, rd_toastoid);
        /* pgstat_info / enabled must be preserved */
        SWAPFIELD(struct PgStat_TableStatus *, pgstat_info);
        SWAPFIELD(bool, pgstat_enabled);
        /* preserve old partition key if we have one */
        if (keep_partkey)
        {
            SWAPFIELD(PartitionKey, rd_partkey);
            SWAPFIELD(MemoryContext, rd_partkeycxt);
        }
        if (newrel->rd_pdcxt != NULL || newrel->rd_pddcxt != NULL)
        {
            /*
             * We are rebuilding a partitioned relation with a non-zero
             * reference count, so we must keep the old partition descriptor
             * around, in case there's a PartitionDirectory with a pointer to
             * it.  This means we can't free the old rd_pdcxt yet.  (This is
             * necessary because RelationGetPartitionDesc hands out direct
             * pointers to the relcache's data structure, unlike our usual
             * practice which is to hand out copies.  We'd have the same
             * problem with rd_partkey, except that we always preserve that
             * once created.)
             *
             * To ensure that it's not leaked completely, re-attach it to the
             * new reldesc, or make it a child of the new reldesc's rd_pdcxt
             * in the unlikely event that there is one already.  (Compare hack
             * in RelationBuildPartitionDesc.)  RelationClose will clean up
             * any such contexts once the reference count reaches zero.
             *
             * In the case where the reference count is zero, this code is not
             * reached, which should be OK because in that case there should
             * be no PartitionDirectory with a pointer to the old entry.
             *
             * Note that newrel and relation have already been swapped, so the
             * "old" partition descriptor is actually the one hanging off of
             * newrel.
             */
            relation->rd_partdesc = NULL;   /* ensure rd_partdesc is invalid */
            relation->rd_partdesc_nodetached = NULL;
            relation->rd_partdesc_nodetached_xmin = InvalidTransactionId;
            if (relation->rd_pdcxt != NULL) /* probably never happens */
                MemoryContextSetParent(newrel->rd_pdcxt, relation->rd_pdcxt);
            else
                relation->rd_pdcxt = newrel->rd_pdcxt;
            if (relation->rd_pddcxt != NULL)
                MemoryContextSetParent(newrel->rd_pddcxt, relation->rd_pddcxt);
            else
                relation->rd_pddcxt = newrel->rd_pddcxt;
            /* drop newrel's pointers so we don't destroy it below */
            newrel->rd_partdesc = NULL;
            newrel->rd_partdesc_nodetached = NULL;
            newrel->rd_partdesc_nodetached_xmin = InvalidTransactionId;
            newrel->rd_pdcxt = NULL;
            newrel->rd_pddcxt = NULL;
        }
 
#undef SWAPFIELD
 
        /* And now we can throw away the temporary entry */
        RelationDestroyRelation(newrel, !keep_tupdesc);
    }
}
 
/*
 * RelationFlushRelation
 *
 *   Rebuild the relation if it is open (refcount > 0), else blow it away.
 *   This is used when we receive a cache invalidation event for the rel.
 */
static void
RelationFlushRelation(Relation relation)
{
    if (relation->rd_createSubid != InvalidSubTransactionId ||
        relation->rd_firstRelfilelocatorSubid != InvalidSubTransactionId)
    {
        /*
         * New relcache entries are always rebuilt, not flushed; else we'd
         * forget the "new" status of the relation.  Ditto for the
         * new-relfilenumber status.
         */
        if (IsTransactionState() && relation->rd_droppedSubid == InvalidSubTransactionId)
        {
            /*
             * The rel could have zero refcnt here, so temporarily increment
             * the refcnt to ensure it's safe to rebuild it.  We can assume
             * that the current transaction has some lock on the rel already.
             */
            RelationIncrementReferenceCount(relation);
            RelationRebuildRelation(relation);
            RelationDecrementReferenceCount(relation);
        }
        else
            RelationInvalidateRelation(relation);
    }
    else
    {
        /*
         * Pre-existing rels can be dropped from the relcache if not open.
         *
         * If the entry is in use, rebuild it if possible.  If we're not
         * inside a valid transaction, we can't do any catalog access so it's
         * not possible to rebuild yet.  Just mark it as invalid in that case,
         * so that the rebuild will occur when the entry is next opened.
         *
         * Note: it's possible that we come here during subtransaction abort,
         * and the reason for wanting to rebuild is that the rel is open in
         * the outer transaction.  In that case it might seem unsafe to not
         * rebuild immediately, since whatever code has the rel already open
         * will keep on using the relcache entry as-is.  However, in such a
         * case the outer transaction should be holding a lock that's
         * sufficient to prevent any significant change in the rel's schema,
         * so the existing entry contents should be good enough for its
         * purposes; at worst we might be behind on statistics updates or the
         * like.  (See also CheckTableNotInUse() and its callers.)
         */
        if (RelationHasReferenceCountZero(relation))
            RelationClearRelation(relation);
        else if (!IsTransactionState())
            RelationInvalidateRelation(relation);
        else if (relation->rd_isnailed && relation->rd_refcnt == 1)
        {
            /*
             * A nailed relation with refcnt == 1 is unused.  We cannot clear
             * it, but there's also no need no need to rebuild it immediately.
             */
            RelationInvalidateRelation(relation);
        }
        else
            RelationRebuildRelation(relation);
    }
}
 
/*
 * RelationForgetRelation - caller reports that it dropped the relation
 */
void
RelationForgetRelation(Oid rid)
{
    Relation    relation;
 
    RelationIdCacheLookup(rid, relation);
 
    if (!PointerIsValid(relation))
        return;                 /* not in cache, nothing to do */
 
    if (!RelationHasReferenceCountZero(relation))
        elog(ERROR, "relation %u is still open", rid);
 
    Assert(relation->rd_droppedSubid == InvalidSubTransactionId);
    if (relation->rd_createSubid != InvalidSubTransactionId ||
        relation->rd_firstRelfilelocatorSubid != InvalidSubTransactionId)
    {
        /*
         * In the event of subtransaction rollback, we must not forget
         * rd_*Subid.  Mark the entry "dropped" and invalidate it, instead of
         * destroying it right away.  (If we're in a top transaction, we could
         * opt to destroy the entry.)
         */
        relation->rd_droppedSubid = GetCurrentSubTransactionId();
        RelationInvalidateRelation(relation);
    }
    else
        RelationClearRelation(relation);
}
 
/*
 *      RelationCacheInvalidateEntry
 *
 *      This routine is invoked for SI cache flush messages.
 *
 * Any relcache entry matching the relid must be flushed.  (Note: caller has
 * already determined that the relid belongs to our database or is a shared
 * relation.)
 *
 * We used to skip local relations, on the grounds that they could
 * not be targets of cross-backend SI update messages; but it seems
 * safer to process them, so that our *own* SI update messages will
 * have the same effects during CommandCounterIncrement for both
 * local and nonlocal relations.
 */
void
RelationCacheInvalidateEntry(Oid relationId)
{
    Relation    relation;
 
    RelationIdCacheLookup(relationId, relation);
 
    if (PointerIsValid(relation))
    {
        relcacheInvalsReceived++;
        RelationFlushRelation(relation);
    }
    else
    {
        int         i;
 
        for (i = 0; i < in_progress_list_len; i++)
            if (in_progress_list[i].reloid == relationId)
                in_progress_list[i].invalidated = true;
    }
}
 
/*
 * RelationCacheInvalidate
 *   Blow away cached relation descriptors that have zero reference counts,
 *   and rebuild those with positive reference counts.  Also reset the smgr
 *   relation cache and re-read relation mapping data.
 *
 *   Apart from debug_discard_caches, this is currently used only to recover
 *   from SI message buffer overflow, so we do not touch relations having
 *   new-in-transaction relfilenumbers; they cannot be targets of cross-backend
 *   SI updates (and our own updates now go through a separate linked list
 *   that isn't limited by the SI message buffer size).
 *
 *   We do this in two phases: the first pass deletes deletable items, and
 *   the second one rebuilds the rebuildable items.  This is essential for
 *   safety, because hash_seq_search only copes with concurrent deletion of
 *   the element it is currently visiting.  If a second SI overflow were to
 *   occur while we are walking the table, resulting in recursive entry to
 *   this routine, we could crash because the inner invocation blows away
 *   the entry next to be visited by the outer scan.  But this way is OK,
 *   because (a) during the first pass we won't process any more SI messages,
 *   so hash_seq_search will complete safely; (b) during the second pass we
 *   only hold onto pointers to nondeletable entries.
 *
 *   The two-phase approach also makes it easy to update relfilenumbers for
 *   mapped relations before we do anything else, and to ensure that the
 *   second pass processes nailed-in-cache items before other nondeletable
 *   items.  This should ensure that system catalogs are up to date before
 *   we attempt to use them to reload information about other open relations.
 *
 *   After those two phases of work having immediate effects, we normally
 *   signal any RelationBuildDesc() on the stack to start over.  However, we
 *   don't do this if called as part of debug_discard_caches.  Otherwise,
 *   RelationBuildDesc() would become an infinite loop.
 */
void
RelationCacheInvalidate(bool debug_discard)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    Relation    relation;
    List       *rebuildFirstList = NIL;
    List       *rebuildList = NIL;
    ListCell   *l;
    int         i;
 
    /*
     * Reload relation mapping data before starting to reconstruct cache.
     */
    RelationMapInvalidateAll();
 
    /* Phase 1 */
    hash_seq_init(&status, RelationIdCache);
 
    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
    {
        relation = idhentry->reldesc;
 
        /*
         * Ignore new relations; no other backend will manipulate them before
         * we commit.  Likewise, before replacing a relation's relfilelocator,
         * we shall have acquired AccessExclusiveLock and drained any
         * applicable pending invalidations.
         */
        if (relation->rd_createSubid != InvalidSubTransactionId ||
            relation->rd_firstRelfilelocatorSubid != InvalidSubTransactionId)
            continue;
 
        relcacheInvalsReceived++;
 
        if (RelationHasReferenceCountZero(relation))
        {
            /* Delete this entry immediately */
            RelationClearRelation(relation);
        }
        else
        {
            /*
             * If it's a mapped relation, immediately update its rd_locator in
             * case its relfilenumber changed.  We must do this during phase 1
             * in case the relation is consulted during rebuild of other
             * relcache entries in phase 2.  It's safe since consulting the
             * map doesn't involve any access to relcache entries.
             */
            if (RelationIsMapped(relation))
            {
                RelationCloseSmgr(relation);
                RelationInitPhysicalAddr(relation);
            }
 
            /*
             * Add this entry to list of stuff to rebuild in second pass.
             * pg_class goes to the front of rebuildFirstList while
             * pg_class_oid_index goes to the back of rebuildFirstList, so
             * they are done first and second respectively.  Other nailed
             * relations go to the front of rebuildList, so they'll be done
             * next in no particular order; and everything else goes to the
             * back of rebuildList.
             */
            if (RelationGetRelid(relation) == RelationRelationId)
                rebuildFirstList = lcons(relation, rebuildFirstList);
            else if (RelationGetRelid(relation) == ClassOidIndexId)
                rebuildFirstList = lappend(rebuildFirstList, relation);
            else if (relation->rd_isnailed)
                rebuildList = lcons(relation, rebuildList);
            else
                rebuildList = lappend(rebuildList, relation);
        }
    }
 
    /*
     * We cannot destroy the SMgrRelations as there might still be references
     * to them, but close the underlying file descriptors.
     */
    smgrreleaseall();
 
    /*
     * Phase 2: rebuild (or invalidate) the items found to need rebuild in
     * phase 1
     */
    foreach(l, rebuildFirstList)
    {
        relation = (Relation) lfirst(l);
        if (!IsTransactionState() || (relation->rd_isnailed && relation->rd_refcnt == 1))
            RelationInvalidateRelation(relation);
        else
            RelationRebuildRelation(relation);
    }
    list_free(rebuildFirstList);
    foreach(l, rebuildList)
    {
        relation = (Relation) lfirst(l);
        if (!IsTransactionState() || (relation->rd_isnailed && relation->rd_refcnt == 1))
            RelationInvalidateRelation(relation);
        else
            RelationRebuildRelation(relation);
    }
    list_free(rebuildList);
 
    if (!debug_discard)
        /* Any RelationBuildDesc() on the stack must start over. */
        for (i = 0; i < in_progress_list_len; i++)
            in_progress_list[i].invalidated = true;
}
 
static void
RememberToFreeTupleDescAtEOX(TupleDesc td)
{
    if (EOXactTupleDescArray == NULL)
    {
        MemoryContext oldcxt;
 
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
        EOXactTupleDescArray = (TupleDesc *) palloc(16 * sizeof(TupleDesc));
        EOXactTupleDescArrayLen = 16;
        NextEOXactTupleDescNum = 0;
        MemoryContextSwitchTo(oldcxt);
    }
    else if (NextEOXactTupleDescNum >= EOXactTupleDescArrayLen)
    {
        int32       newlen = EOXactTupleDescArrayLen * 2;
 
        Assert(EOXactTupleDescArrayLen > 0);
 
        EOXactTupleDescArray = (TupleDesc *) repalloc(EOXactTupleDescArray,
                                                      newlen * sizeof(TupleDesc));
        EOXactTupleDescArrayLen = newlen;
    }
 
    EOXactTupleDescArray[NextEOXactTupleDescNum++] = td;
}
 
#ifdef USE_ASSERT_CHECKING
static void
AssertPendingSyncConsistency(Relation relation)
{
    bool        relcache_verdict =
        RelationIsPermanent(relation) &&
        ((relation->rd_createSubid != InvalidSubTransactionId &&
          RELKIND_HAS_STORAGE(relation->rd_rel->relkind)) ||
         relation->rd_firstRelfilelocatorSubid != InvalidSubTransactionId);
 
    Assert(relcache_verdict == RelFileLocatorSkippingWAL(relation->rd_locator));
 
    if (relation->rd_droppedSubid != InvalidSubTransactionId)
        Assert(!relation->rd_isvalid &&
               (relation->rd_createSubid != InvalidSubTransactionId ||
                relation->rd_firstRelfilelocatorSubid != InvalidSubTransactionId));
}
 
/*
 * AssertPendingSyncs_RelationCache
 *
 *  Assert that relcache.c and storage.c agree on whether to skip WAL.
 */
void
AssertPendingSyncs_RelationCache(void)
{
    HASH_SEQ_STATUS status;
    LOCALLOCK  *locallock;
    Relation   *rels;
    int         maxrels;
    int         nrels;
    RelIdCacheEnt *idhentry;
    int         i;
 
    /*
     * Open every relation that this transaction has locked.  If, for some
     * relation, storage.c is skipping WAL and relcache.c is not skipping WAL,
     * a CommandCounterIncrement() typically yields a local invalidation
     * message that destroys the relcache entry.  By recreating such entries
     * here, we detect the problem.
     */
    PushActiveSnapshot(GetTransactionSnapshot());
    maxrels = 1;
    rels = palloc(maxrels * sizeof(*rels));
    nrels = 0;
    hash_seq_init(&status, GetLockMethodLocalHash());
    while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
    {
        Oid         relid;
        Relation    r;
 
        if (locallock->nLocks <= 0)
            continue;
        if ((LockTagType) locallock->tag.lock.locktag_type !=
            LOCKTAG_RELATION)
            continue;
        relid = ObjectIdGetDatum(locallock->tag.lock.locktag_field2);
        r = RelationIdGetRelation(relid);
        if (!RelationIsValid(r))
            continue;
        if (nrels >= maxrels)
        {
            maxrels *= 2;
            rels = repalloc(rels, maxrels * sizeof(*rels));
        }
        rels[nrels++] = r;
    }
 
    hash_seq_init(&status, RelationIdCache);
    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        AssertPendingSyncConsistency(idhentry->reldesc);
 
    for (i = 0; i < nrels; i++)
        RelationClose(rels[i]);
    PopActiveSnapshot();
}
#endif
 
/*
 * AtEOXact_RelationCache
 *
 *  Clean up the relcache at main-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 * In the case of abort, we don't want to try to rebuild any invalidated
 * cache entries (since we can't safely do database accesses).  Therefore
 * we must reset refcnts before handling pending invalidations.
 *
 * As of PostgreSQL 8.1, relcache refcnts should get released by the
 * ResourceOwner mechanism.  This routine just does a debugging
 * cross-check that no pins remain.  However, we also need to do special
 * cleanup when the current transaction created any relations or made use
 * of forced index lists.
 */
void
AtEOXact_RelationCache(bool isCommit)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    int         i;
 
    /*
     * Forget in_progress_list.  This is relevant when we're aborting due to
     * an error during RelationBuildDesc().
     */
    Assert(in_progress_list_len == 0 || !isCommit);
    in_progress_list_len = 0;
 
    /*
     * Unless the eoxact_list[] overflowed, we only need to examine the rels
     * listed in it.  Otherwise fall back on a hash_seq_search scan.
     *
     * For simplicity, eoxact_list[] entries are not deleted till end of
     * top-level transaction, even though we could remove them at
     * subtransaction end in some cases, or remove relations from the list if
     * they are cleared for other reasons.  Therefore we should expect the
     * case that list entries are not found in the hashtable; if not, there's
     * nothing to do for them.
     */
    if (eoxact_list_overflowed)
    {
        hash_seq_init(&status, RelationIdCache);
        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
            AtEOXact_cleanup(idhentry->reldesc, isCommit);
        }
    }
    else
    {
        for (i = 0; i < eoxact_list_len; i++)
        {
            idhentry = (RelIdCacheEnt *) hash_search(RelationIdCache,
                                                     &eoxact_list[i],
                                                     HASH_FIND,
                                                     NULL);
            if (idhentry != NULL)
                AtEOXact_cleanup(idhentry->reldesc, isCommit);
        }
    }
 
    if (EOXactTupleDescArrayLen > 0)
    {
        Assert(EOXactTupleDescArray != NULL);
        for (i = 0; i < NextEOXactTupleDescNum; i++)
            FreeTupleDesc(EOXactTupleDescArray[i]);
        pfree(EOXactTupleDescArray);
        EOXactTupleDescArray = NULL;
    }
 
    /* Now we're out of the transaction and can clear the lists */
    eoxact_list_len = 0;
    eoxact_list_overflowed = false;
    NextEOXactTupleDescNum = 0;
    EOXactTupleDescArrayLen = 0;
}
 
/*
 * AtEOXact_cleanup
 *
 *  Clean up a single rel at main-transaction commit or abort
 *
 * NB: this processing must be idempotent, because EOXactListAdd() doesn't
 * bother to prevent duplicate entries in eoxact_list[].
 */
static void
AtEOXact_cleanup(Relation relation, bool isCommit)
{
    bool        clear_relcache = false;
 
    /*
     * The relcache entry's ref count should be back to its normal
     * not-in-a-transaction state: 0 unless it's nailed in cache.
     *
     * In bootstrap mode, this is NOT true, so don't check it --- the
     * bootstrap code expects relations to stay open across start/commit
     * transaction calls.  (That seems bogus, but it's not worth fixing.)
     *
     * Note: ideally this check would be applied to every relcache entry, not
     * just those that have eoxact work to do.  But it's not worth forcing a
     * scan of the whole relcache just for this.  (Moreover, doing so would
     * mean that assert-enabled testing never tests the hash_search code path
     * above, which seems a bad idea.)
     */
#ifdef USE_ASSERT_CHECKING
    if (!IsBootstrapProcessingMode())
    {
        int         expected_refcnt;
 
        expected_refcnt = relation->rd_isnailed ? 1 : 0;
        Assert(relation->rd_refcnt == expected_refcnt);
    }
#endif
 
    /*
     * Is the relation live after this transaction ends?
     *
     * During commit, clear the relcache entry if it is preserved after
     * relation drop, in order not to orphan the entry.  During rollback,
     * clear the relcache entry if the relation is created in the current
     * transaction since it isn't interesting any longer once we are out of
     * the transaction.
     */
    clear_relcache =
        (isCommit ?
         relation->rd_droppedSubid != InvalidSubTransactionId :
         relation->rd_createSubid != InvalidSubTransactionId);
 
    /*
     * Since we are now out of the transaction, reset the subids to zero. That
     * also lets RelationClearRelation() drop the relcache entry.
     */
    relation->rd_createSubid = InvalidSubTransactionId;
    relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    relation->rd_droppedSubid = InvalidSubTransactionId;
 
    if (clear_relcache)
    {
        if (RelationHasReferenceCountZero(relation))
        {
            RelationClearRelation(relation);
            return;
        }
        else
        {
            /*
             * Hmm, somewhere there's a (leaked?) reference to the relation.
             * We daren't remove the entry for fear of dereferencing a
             * dangling pointer later.  Bleat, and mark it as not belonging to
             * the current transaction.  Hopefully it'll get cleaned up
             * eventually.  This must be just a WARNING to avoid
             * error-during-error-recovery loops.
             */
            elog(WARNING, "cannot remove relcache entry for \"%s\" because it has nonzero refcount",
                 RelationGetRelationName(relation));
        }
    }
}
 
/*
 * AtEOSubXact_RelationCache
 *
 *  Clean up the relcache at sub-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 */
void
AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
                          SubTransactionId parentSubid)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    int         i;
 
    /*
     * Forget in_progress_list.  This is relevant when we're aborting due to
     * an error during RelationBuildDesc().  We don't commit subtransactions
     * during RelationBuildDesc().
     */
    Assert(in_progress_list_len == 0 || !isCommit);
    in_progress_list_len = 0;
 
    /*
     * Unless the eoxact_list[] overflowed, we only need to examine the rels
     * listed in it.  Otherwise fall back on a hash_seq_search scan.  Same
     * logic as in AtEOXact_RelationCache.
     */
    if (eoxact_list_overflowed)
    {
        hash_seq_init(&status, RelationIdCache);
        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
            AtEOSubXact_cleanup(idhentry->reldesc, isCommit,
                                mySubid, parentSubid);
        }
    }
    else
    {
        for (i = 0; i < eoxact_list_len; i++)
        {
            idhentry = (RelIdCacheEnt *) hash_search(RelationIdCache,
                                                     &eoxact_list[i],
                                                     HASH_FIND,
                                                     NULL);
            if (idhentry != NULL)
                AtEOSubXact_cleanup(idhentry->reldesc, isCommit,
                                    mySubid, parentSubid);
        }
    }
 
    /* Don't reset the list; we still need more cleanup later */
}
 
/*
 * AtEOSubXact_cleanup
 *
 *  Clean up a single rel at subtransaction commit or abort
 *
 * NB: this processing must be idempotent, because EOXactListAdd() doesn't
 * bother to prevent duplicate entries in eoxact_list[].
 */
static void
AtEOSubXact_cleanup(Relation relation, bool isCommit,
                    SubTransactionId mySubid, SubTransactionId parentSubid)
{
    /*
     * Is it a relation created in the current subtransaction?
     *
     * During subcommit, mark it as belonging to the parent, instead, as long
     * as it has not been dropped. Otherwise simply delete the relcache entry.
     * --- it isn't interesting any longer.
     */
    if (relation->rd_createSubid == mySubid)
    {
        /*
         * Valid rd_droppedSubid means the corresponding relation is dropped
         * but the relcache entry is preserved for at-commit pending sync. We
         * need to drop it explicitly here not to make the entry orphan.
         */
        Assert(relation->rd_droppedSubid == mySubid ||
               relation->rd_droppedSubid == InvalidSubTransactionId);
        if (isCommit && relation->rd_droppedSubid == InvalidSubTransactionId)
            relation->rd_createSubid = parentSubid;
        else if (RelationHasReferenceCountZero(relation))
        {
            /* allow the entry to be removed */
            relation->rd_createSubid = InvalidSubTransactionId;
            relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
            relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
            relation->rd_droppedSubid = InvalidSubTransactionId;
            RelationClearRelation(relation);
            return;
        }
        else
        {
            /*
             * Hmm, somewhere there's a (leaked?) reference to the relation.
             * We daren't remove the entry for fear of dereferencing a
             * dangling pointer later.  Bleat, and transfer it to the parent
             * subtransaction so we can try again later.  This must be just a
             * WARNING to avoid error-during-error-recovery loops.
             */
            relation->rd_createSubid = parentSubid;
            elog(WARNING, "cannot remove relcache entry for \"%s\" because it has nonzero refcount",
                 RelationGetRelationName(relation));
        }
    }
 
    /*
     * Likewise, update or drop any new-relfilenumber-in-subtransaction record
     * or drop record.
     */
    if (relation->rd_newRelfilelocatorSubid == mySubid)
    {
        if (isCommit)
            relation->rd_newRelfilelocatorSubid = parentSubid;
        else
            relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
    }
 
    if (relation->rd_firstRelfilelocatorSubid == mySubid)
    {
        if (isCommit)
            relation->rd_firstRelfilelocatorSubid = parentSubid;
        else
            relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    }
 
    if (relation->rd_droppedSubid == mySubid)
    {
        if (isCommit)
            relation->rd_droppedSubid = parentSubid;
        else
            relation->rd_droppedSubid = InvalidSubTransactionId;
    }
}
 
 
/*
 *      RelationBuildLocalRelation
 *          Build a relcache entry for an about-to-be-created relation,
 *          and enter it into the relcache.
 */
Relation
RelationBuildLocalRelation(const char *relname,
                           Oid relnamespace,
                           TupleDesc tupDesc,
                           Oid relid,
                           Oid accessmtd,
                           RelFileNumber relfilenumber,
                           Oid reltablespace,
                           bool shared_relation,
                           bool mapped_relation,
                           char relpersistence,
                           char relkind)
{
    Relation    rel;
    MemoryContext oldcxt;
    int         natts = tupDesc->natts;
    int         i;
    bool        has_not_null;
    bool        nailit;
 
    Assert(natts >= 0);
 
    /*
     * check for creation of a rel that must be nailed in cache.
     *
     * XXX this list had better match the relations specially handled in
     * RelationCacheInitializePhase2/3.
     */
    switch (relid)
    {
        case DatabaseRelationId:
        case AuthIdRelationId:
        case AuthMemRelationId:
        case RelationRelationId:
        case AttributeRelationId:
        case ProcedureRelationId:
        case TypeRelationId:
            nailit = true;
            break;
        default:
            nailit = false;
            break;
    }
 
    /*
     * check that hardwired list of shared rels matches what's in the
     * bootstrap .bki file.  If you get a failure here during initdb, you
     * probably need to fix IsSharedRelation() to match whatever you've done
     * to the set of shared relations.
     */
    if (shared_relation != IsSharedRelation(relid))
        elog(ERROR, "shared_relation flag for \"%s\" does not match IsSharedRelation(%u)",
             relname, relid);
 
    /* Shared relations had better be mapped, too */
    Assert(mapped_relation || !shared_relation);
 
    /*
     * switch to the cache context to create the relcache entry.
     */
    if (!CacheMemoryContext)
        CreateCacheMemoryContext();
 
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
    /*
     * allocate a new relation descriptor and fill in basic state fields.
     */
    rel = (Relation) palloc0(sizeof(RelationData));
 
    /* make sure relation is marked as having no open file yet */
    rel->rd_smgr = NULL;
 
    /* mark it nailed if appropriate */
    rel->rd_isnailed = nailit;
 
    rel->rd_refcnt = nailit ? 1 : 0;
 
    /* it's being created in this transaction */
    rel->rd_createSubid = GetCurrentSubTransactionId();
    rel->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
    rel->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
    rel->rd_droppedSubid = InvalidSubTransactionId;
 
    /*
     * create a new tuple descriptor from the one passed in.  We do this
     * partly to copy it into the cache context, and partly because the new
     * relation can't have any defaults or constraints yet; they have to be
     * added in later steps, because they require additions to multiple system
     * catalogs.  We can copy attnotnull constraints here, however.
     */
    rel->rd_att = CreateTupleDescCopy(tupDesc);
    rel->rd_att->tdrefcount = 1;    /* mark as refcounted */
    has_not_null = false;
    for (i = 0; i < natts; i++)
    {
        Form_pg_attribute satt = TupleDescAttr(tupDesc, i);
        Form_pg_attribute datt = TupleDescAttr(rel->rd_att, i);
 
        datt->attidentity = satt->attidentity;
        datt->attgenerated = satt->attgenerated;
        datt->attnotnull = satt->attnotnull;
        has_not_null |= satt->attnotnull;
        populate_compact_attribute(rel->rd_att, i);
    }
 
    if (has_not_null)
    {
        TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));
 
        constr->has_not_null = true;
        rel->rd_att->constr = constr;
    }
 
    /*
     * initialize relation tuple form (caller may add/override data later)
     */
    rel->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);
 
    namestrcpy(&rel->rd_rel->relname, relname);
    rel->rd_rel->relnamespace = relnamespace;
 
    rel->rd_rel->relkind = relkind;
    rel->rd_rel->relnatts = natts;
    rel->rd_rel->reltype = InvalidOid;
    /* needed when bootstrapping: */
    rel->rd_rel->relowner = BOOTSTRAP_SUPERUSERID;
 
    /* set up persistence and relcache fields dependent on it */
    rel->rd_rel->relpersistence = relpersistence;
    switch (relpersistence)
    {
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            rel->rd_backend = INVALID_PROC_NUMBER;
            rel->rd_islocaltemp = false;
            break;
        case RELPERSISTENCE_TEMP:
            Assert(isTempOrTempToastNamespace(relnamespace));
            rel->rd_backend = ProcNumberForTempRelations();
            rel->rd_islocaltemp = true;
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c", relpersistence);
            break;
    }
 
    /* if it's a materialized view, it's not populated initially */
    if (relkind == RELKIND_MATVIEW)
        rel->rd_rel->relispopulated = false;
    else
        rel->rd_rel->relispopulated = true;
 
    /* set replica identity -- system catalogs and non-tables don't have one */
    if (!IsCatalogNamespace(relnamespace) &&
        (relkind == RELKIND_RELATION ||
         relkind == RELKIND_MATVIEW ||
         relkind == RELKIND_PARTITIONED_TABLE))
        rel->rd_rel->relreplident = REPLICA_IDENTITY_DEFAULT;
    else
        rel->rd_rel->relreplident = REPLICA_IDENTITY_NOTHING;
 
    /*
     * Insert relation physical and logical identifiers (OIDs) into the right
     * places.  For a mapped relation, we set relfilenumber to zero and rely
     * on RelationInitPhysicalAddr to consult the map.
     */
    rel->rd_rel->relisshared = shared_relation;
 
    RelationGetRelid(rel) = relid;
 
    for (i = 0; i < natts; i++)
        TupleDescAttr(rel->rd_att, i)->attrelid = relid;
 
    rel->rd_rel->reltablespace = reltablespace;
 
    if (mapped_relation)
    {
        rel->rd_rel->relfilenode = InvalidRelFileNumber;
        /* Add it to the active mapping information */
        RelationMapUpdateMap(relid, relfilenumber, shared_relation, true);
    }
    else
        rel->rd_rel->relfilenode = relfilenumber;
 
    RelationInitLockInfo(rel);  /* see lmgr.c */
 
    RelationInitPhysicalAddr(rel);
 
    rel->rd_rel->relam = accessmtd;
 
    /*
     * RelationInitTableAccessMethod will do syscache lookups, so we mustn't
     * run it in CacheMemoryContext.  Fortunately, the remaining steps don't
     * require a long-lived current context.
     */
    MemoryContextSwitchTo(oldcxt);
 
    if (RELKIND_HAS_TABLE_AM(relkind) || relkind == RELKIND_SEQUENCE)
        RelationInitTableAccessMethod(rel);
 
    /*
     * Leave index access method uninitialized, because the pg_index row has
     * not been inserted at this stage of index creation yet.  The cache
     * invalidation after pg_index row has been inserted will initialize it.
     */
 
    /*
     * Okay to insert into the relcache hash table.
     *
     * Ordinarily, there should certainly not be an existing hash entry for
     * the same OID; but during bootstrap, when we create a "real" relcache
     * entry for one of the bootstrap relations, we'll be overwriting the
     * phony one created with formrdesc.  So allow that to happen for nailed
     * rels.
     */
    RelationCacheInsert(rel, nailit);
 
    /*
     * Flag relation as needing eoxact cleanup (to clear rd_createSubid). We
     * can't do this before storing relid in it.
     */
    EOXactListAdd(rel);
 
    /* It's fully valid */
    rel->rd_isvalid = true;
 
    /*
     * Caller expects us to pin the returned entry.
     */
    RelationIncrementReferenceCount(rel);
 
    return rel;
}
 
 
/*
 * RelationSetNewRelfilenumber
 *
 * Assign a new relfilenumber (physical file name), and possibly a new
 * persistence setting, to the relation.
 *
 * This allows a full rewrite of the relation to be done with transactional
 * safety (since the filenumber assignment can be rolled back).  Note however
 * that there is no simple way to access the relation's old data for the
 * remainder of the current transaction.  This limits the usefulness to cases
 * such as TRUNCATE or rebuilding an index from scratch.
 *
 * Caller must already hold exclusive lock on the relation.
 */
void
RelationSetNewRelfilenumber(Relation relation, char persistence)
{
    RelFileNumber newrelfilenumber;
    Relation    pg_class;
    ItemPointerData otid;
    HeapTuple   tuple;
    Form_pg_class classform;
    MultiXactId minmulti = InvalidMultiXactId;
    TransactionId freezeXid = InvalidTransactionId;
    RelFileLocator newrlocator;
 
    if (!IsBinaryUpgrade)
    {
        /* Allocate a new relfilenumber */
        newrelfilenumber = GetNewRelFileNumber(relation->rd_rel->reltablespace,
                                               NULL, persistence);
    }
    else if (relation->rd_rel->relkind == RELKIND_INDEX)
    {
        if (!OidIsValid(binary_upgrade_next_index_pg_class_relfilenumber))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("index relfilenumber value not set when in binary upgrade mode")));
 
        newrelfilenumber = binary_upgrade_next_index_pg_class_relfilenumber;
        binary_upgrade_next_index_pg_class_relfilenumber = InvalidOid;
    }
    else if (relation->rd_rel->relkind == RELKIND_RELATION)
    {
        if (!OidIsValid(binary_upgrade_next_heap_pg_class_relfilenumber))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("heap relfilenumber value not set when in binary upgrade mode")));
 
        newrelfilenumber = binary_upgrade_next_heap_pg_class_relfilenumber;
        binary_upgrade_next_heap_pg_class_relfilenumber = InvalidOid;
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("unexpected request for new relfilenumber in binary upgrade mode")));
 
    /*
     * Get a writable copy of the pg_class tuple for the given relation.
     */
    pg_class = table_open(RelationRelationId, RowExclusiveLock);
 
    tuple = SearchSysCacheLockedCopy1(RELOID,
                                      ObjectIdGetDatum(RelationGetRelid(relation)));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "could not find tuple for relation %u",
             RelationGetRelid(relation));
    otid = tuple->t_self;
    classform = (Form_pg_class) GETSTRUCT(tuple);
 
    /*
     * Schedule unlinking of the old storage at transaction commit, except
     * when performing a binary upgrade, when we must do it immediately.
     */
    if (IsBinaryUpgrade)
    {
        SMgrRelation srel;
 
        /*
         * During a binary upgrade, we use this code path to ensure that
         * pg_largeobject and its index have the same relfilenumbers as in the
         * old cluster. This is necessary because pg_upgrade treats
         * pg_largeobject like a user table, not a system table. It is however
         * possible that a table or index may need to end up with the same
         * relfilenumber in the new cluster as what it had in the old cluster.
         * Hence, we can't wait until commit time to remove the old storage.
         *
         * In general, this function needs to have transactional semantics,
         * and removing the old storage before commit time surely isn't.
         * However, it doesn't really matter, because if a binary upgrade
         * fails at this stage, the new cluster will need to be recreated
         * anyway.
         */
        srel = smgropen(relation->rd_locator, relation->rd_backend);
        smgrdounlinkall(&srel, 1, false);
        smgrclose(srel);
    }
    else
    {
        /* Not a binary upgrade, so just schedule it to happen later. */
        RelationDropStorage(relation);
    }
 
    /*
     * Create storage for the main fork of the new relfilenumber.  If it's a
     * table-like object, call into the table AM to do so, which'll also
     * create the table's init fork if needed.
     *
     * NOTE: If relevant for the AM, any conflict in relfilenumber value will
     * be caught here, if GetNewRelFileNumber messes up for any reason.
     */
    newrlocator = relation->rd_locator;
    newrlocator.relNumber = newrelfilenumber;
 
    if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
    {
        table_relation_set_new_filelocator(relation, &newrlocator,
                                           persistence,
                                           &freezeXid, &minmulti);
    }
    else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
    {
        /* handle these directly, at least for now */
        SMgrRelation srel;
 
        srel = RelationCreateStorage(newrlocator, persistence, true);
        smgrclose(srel);
    }
    else
    {
        /* we shouldn't be called for anything else */
        elog(ERROR, "relation \"%s\" does not have storage",
             RelationGetRelationName(relation));
    }
 
    /*
     * If we're dealing with a mapped index, pg_class.relfilenode doesn't
     * change; instead we have to send the update to the relation mapper.
     *
     * For mapped indexes, we don't actually change the pg_class entry at all;
     * this is essential when reindexing pg_class itself.  That leaves us with
     * possibly-inaccurate values of relpages etc, but those will be fixed up
     * later.
     */
    if (RelationIsMapped(relation))
    {
        /* This case is only supported for indexes */
        Assert(relation->rd_rel->relkind == RELKIND_INDEX);
 
        /* Since we're not updating pg_class, these had better not change */
        Assert(classform->relfrozenxid == freezeXid);
        Assert(classform->relminmxid == minmulti);
        Assert(classform->relpersistence == persistence);
 
        /*
         * In some code paths it's possible that the tuple update we'd
         * otherwise do here is the only thing that would assign an XID for
         * the current transaction.  However, we must have an XID to delete
         * files, so make sure one is assigned.
         */
        (void) GetCurrentTransactionId();
 
        /* Do the deed */
        RelationMapUpdateMap(RelationGetRelid(relation),
                             newrelfilenumber,
                             relation->rd_rel->relisshared,
                             false);
 
        /* Since we're not updating pg_class, must trigger inval manually */
        CacheInvalidateRelcache(relation);
    }
    else
    {
        /* Normal case, update the pg_class entry */
        classform->relfilenode = newrelfilenumber;
 
        /* relpages etc. never change for sequences */
        if (relation->rd_rel->relkind != RELKIND_SEQUENCE)
        {
            classform->relpages = 0;    /* it's empty until further notice */
            classform->reltuples = -1;
            classform->relallvisible = 0;
        }
        classform->relfrozenxid = freezeXid;
        classform->relminmxid = minmulti;
        classform->relpersistence = persistence;
 
        CatalogTupleUpdate(pg_class, &otid, tuple);
    }
 
    UnlockTuple(pg_class, &otid, InplaceUpdateTupleLock);
    heap_freetuple(tuple);
 
    table_close(pg_class, RowExclusiveLock);
 
    /*
     * Make the pg_class row change or relation map change visible.  This will
     * cause the relcache entry to get updated, too.
     */
    CommandCounterIncrement();
 
    RelationAssumeNewRelfilelocator(relation);
}
 
/*
 * RelationAssumeNewRelfilelocator
 *
 * Code that modifies pg_class.reltablespace or pg_class.relfilenode must call
 * this.  The call shall precede any code that might insert WAL records whose
 * replay would modify bytes in the new RelFileLocator, and the call shall follow
 * any WAL modifying bytes in the prior RelFileLocator.  See struct RelationData.
 * Ideally, call this as near as possible to the CommandCounterIncrement()
 * that makes the pg_class change visible (before it or after it); that
 * minimizes the chance of future development adding a forbidden WAL insertion
 * between RelationAssumeNewRelfilelocator() and CommandCounterIncrement().
 */
void
RelationAssumeNewRelfilelocator(Relation relation)
{
    relation->rd_newRelfilelocatorSubid = GetCurrentSubTransactionId();
    if (relation->rd_firstRelfilelocatorSubid == InvalidSubTransactionId)
        relation->rd_firstRelfilelocatorSubid = relation->rd_newRelfilelocatorSubid;
 
    /* Flag relation as needing eoxact cleanup (to clear these fields) */
    EOXactListAdd(relation);
}
 
 
/*
 *      RelationCacheInitialize
 *
 *      This initializes the relation descriptor cache.  At the time
 *      that this is invoked, we can't do database access yet (mainly
 *      because the transaction subsystem is not up); all we are doing
 *      is making an empty cache hashtable.  This must be done before
 *      starting the initialization transaction, because otherwise
 *      AtEOXact_RelationCache would crash if that transaction aborts
 *      before we can get the relcache set up.
 */
 
#define INITRELCACHESIZE        400
 
void
RelationCacheInitialize(void)
{
    HASHCTL     ctl;
    int         allocsize;
 
    /*
     * make sure cache memory context exists
     */
    if (!CacheMemoryContext)
        CreateCacheMemoryContext();
 
    /*
     * create hashtable that indexes the relcache
     */
    ctl.keysize = sizeof(Oid);
    ctl.entrysize = sizeof(RelIdCacheEnt);
    RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
                                  &ctl, HASH_ELEM | HASH_BLOBS);
 
    /*
     * reserve enough in_progress_list slots for many cases
     */
    allocsize = 4;
    in_progress_list =
        MemoryContextAlloc(CacheMemoryContext,
                           allocsize * sizeof(*in_progress_list));
    in_progress_list_maxlen = allocsize;
 
    /*
     * relation mapper needs to be initialized too
     */
    RelationMapInitialize();
}
 
/*
 *      RelationCacheInitializePhase2
 *
 *      This is called to prepare for access to shared catalogs during startup.
 *      We must at least set up nailed reldescs for pg_database, pg_authid,
 *      pg_auth_members, and pg_shseclabel. Ideally we'd like to have reldescs
 *      for their indexes, too.  We attempt to load this information from the
 *      shared relcache init file.  If that's missing or broken, just make
 *      phony entries for the catalogs themselves.
 *      RelationCacheInitializePhase3 will clean up as needed.
 */
void
RelationCacheInitializePhase2(void)
{
    MemoryContext oldcxt;
 
    /*
     * relation mapper needs initialized too
     */
    RelationMapInitializePhase2();
 
    /*
     * In bootstrap mode, the shared catalogs aren't there yet anyway, so do
     * nothing.
     */
    if (IsBootstrapProcessingMode())
        return;
 
    /*
     * switch to cache memory context
     */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
    /*
     * Try to load the shared relcache cache file.  If unsuccessful, bootstrap
     * the cache with pre-made descriptors for the critical shared catalogs.
     */
    if (!load_relcache_init_file(true))
    {
        formrdesc("pg_database", DatabaseRelation_Rowtype_Id, true,
                  Natts_pg_database, Desc_pg_database);
        formrdesc("pg_authid", AuthIdRelation_Rowtype_Id, true,
                  Natts_pg_authid, Desc_pg_authid);
        formrdesc("pg_auth_members", AuthMemRelation_Rowtype_Id, true,
                  Natts_pg_auth_members, Desc_pg_auth_members);
        formrdesc("pg_shseclabel", SharedSecLabelRelation_Rowtype_Id, true,
                  Natts_pg_shseclabel, Desc_pg_shseclabel);
        formrdesc("pg_subscription", SubscriptionRelation_Rowtype_Id, true,
                  Natts_pg_subscription, Desc_pg_subscription);
 
#define NUM_CRITICAL_SHARED_RELS    5   /* fix if you change list above */
    }
 
    MemoryContextSwitchTo(oldcxt);
}
 
/*
 *      RelationCacheInitializePhase3
 *
 *      This is called as soon as the catcache and transaction system
 *      are functional and we have determined MyDatabaseId.  At this point
 *      we can actually read data from the database's system catalogs.
 *      We first try to read pre-computed relcache entries from the local
 *      relcache init file.  If that's missing or broken, make phony entries
 *      for the minimum set of nailed-in-cache relations.  Then (unless
 *      bootstrapping) make sure we have entries for the critical system
 *      indexes.  Once we've done all this, we have enough infrastructure to
 *      open any system catalog or use any catcache.  The last step is to
 *      rewrite the cache files if needed.
 */
void
RelationCacheInitializePhase3(void)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    MemoryContext oldcxt;
    bool        needNewCacheFile = !criticalSharedRelcachesBuilt;
 
    /*
     * relation mapper needs initialized too
     */
    RelationMapInitializePhase3();
 
    /*
     * switch to cache memory context
     */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
    /*
     * Try to load the local relcache cache file.  If unsuccessful, bootstrap
     * the cache with pre-made descriptors for the critical "nailed-in" system
     * catalogs.
     */
    if (IsBootstrapProcessingMode() ||
        !load_relcache_init_file(false))
    {
        needNewCacheFile = true;
 
        formrdesc("pg_class", RelationRelation_Rowtype_Id, false,
                  Natts_pg_class, Desc_pg_class);
        formrdesc("pg_attribute", AttributeRelation_Rowtype_Id, false,
                  Natts_pg_attribute, Desc_pg_attribute);
        formrdesc("pg_proc", ProcedureRelation_Rowtype_Id, false,
                  Natts_pg_proc, Desc_pg_proc);
        formrdesc("pg_type", TypeRelation_Rowtype_Id, false,
                  Natts_pg_type, Desc_pg_type);
 
#define NUM_CRITICAL_LOCAL_RELS 4   /* fix if you change list above */
    }
 
    MemoryContextSwitchTo(oldcxt);
 
    /* In bootstrap mode, the faked-up formrdesc info is all we'll have */
    if (IsBootstrapProcessingMode())
        return;
 
    /*
     * If we didn't get the critical system indexes loaded into relcache, do
     * so now.  These are critical because the catcache and/or opclass cache
     * depend on them for fetches done during relcache load.  Thus, we have an
     * infinite-recursion problem.  We can break the recursion by doing
     * heapscans instead of indexscans at certain key spots. To avoid hobbling
     * performance, we only want to do that until we have the critical indexes
     * loaded into relcache.  Thus, the flag criticalRelcachesBuilt is used to
     * decide whether to do heapscan or indexscan at the key spots, and we set
     * it true after we've loaded the critical indexes.
     *
     * The critical indexes are marked as "nailed in cache", partly to make it
     * easy for load_relcache_init_file to count them, but mainly because we
     * cannot flush and rebuild them once we've set criticalRelcachesBuilt to
     * true.  (NOTE: perhaps it would be possible to reload them by
     * temporarily setting criticalRelcachesBuilt to false again.  For now,
     * though, we just nail 'em in.)
     *
     * RewriteRelRulenameIndexId and TriggerRelidNameIndexId are not critical
     * in the same way as the others, because the critical catalogs don't
     * (currently) have any rules or triggers, and so these indexes can be
     * rebuilt without inducing recursion.  However they are used during
     * relcache load when a rel does have rules or triggers, so we choose to
     * nail them for performance reasons.
     */
    if (!criticalRelcachesBuilt)
    {
        load_critical_index(ClassOidIndexId,
                            RelationRelationId);
        load_critical_index(AttributeRelidNumIndexId,
                            AttributeRelationId);
        load_critical_index(IndexRelidIndexId,
                            IndexRelationId);
        load_critical_index(OpclassOidIndexId,
                            OperatorClassRelationId);
        load_critical_index(AccessMethodProcedureIndexId,
                            AccessMethodProcedureRelationId);
        load_critical_index(RewriteRelRulenameIndexId,
                            RewriteRelationId);
        load_critical_index(TriggerRelidNameIndexId,
                            TriggerRelationId);
 
#define NUM_CRITICAL_LOCAL_INDEXES  7   /* fix if you change list above */
 
        criticalRelcachesBuilt = true;
    }
 
    /*
     * Process critical shared indexes too.
     *
     * DatabaseNameIndexId isn't critical for relcache loading, but rather for
     * initial lookup of MyDatabaseId, without which we'll never find any
     * non-shared catalogs at all.  Autovacuum calls InitPostgres with a
     * database OID, so it instead depends on DatabaseOidIndexId.  We also
     * need to nail up some indexes on pg_authid and pg_auth_members for use
     * during client authentication.  SharedSecLabelObjectIndexId isn't
     * critical for the core system, but authentication hooks might be
     * interested in it.
     */
    if (!criticalSharedRelcachesBuilt)
    {
        load_critical_index(DatabaseNameIndexId,
                            DatabaseRelationId);
        load_critical_index(DatabaseOidIndexId,
                            DatabaseRelationId);
        load_critical_index(AuthIdRolnameIndexId,
                            AuthIdRelationId);
        load_critical_index(AuthIdOidIndexId,
                            AuthIdRelationId);
        load_critical_index(AuthMemMemRoleIndexId,
                            AuthMemRelationId);
        load_critical_index(SharedSecLabelObjectIndexId,
                            SharedSecLabelRelationId);
 
#define NUM_CRITICAL_SHARED_INDEXES 6   /* fix if you change list above */
 
        criticalSharedRelcachesBuilt = true;
    }
 
    /*
     * Now, scan all the relcache entries and update anything that might be
     * wrong in the results from formrdesc or the relcache cache file. If we
     * faked up relcache entries using formrdesc, then read the real pg_class
     * rows and replace the fake entries with them. Also, if any of the
     * relcache entries have rules, triggers, or security policies, load that
     * info the hard way since it isn't recorded in the cache file.
     *
     * Whenever we access the catalogs to read data, there is a possibility of
     * a shared-inval cache flush causing relcache entries to be removed.
     * Since hash_seq_search only guarantees to still work after the *current*
     * entry is removed, it's unsafe to continue the hashtable scan afterward.
     * We handle this by restarting the scan from scratch after each access.
     * This is theoretically O(N^2), but the number of entries that actually
     * need to be fixed is small enough that it doesn't matter.
     */
    hash_seq_init(&status, RelationIdCache);
 
    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
    {
        Relation    relation = idhentry->reldesc;
        bool        restart = false;
 
        /*
         * Make sure *this* entry doesn't get flushed while we work with it.
         */
        RelationIncrementReferenceCount(relation);
 
        /*
         * If it's a faked-up entry, read the real pg_class tuple.
         */
        if (relation->rd_rel->relowner == InvalidOid)
        {
            HeapTuple   htup;
            Form_pg_class relp;
 
            htup = SearchSysCache1(RELOID,
                                   ObjectIdGetDatum(RelationGetRelid(relation)));
            if (!HeapTupleIsValid(htup))
                ereport(FATAL,
                        errcode(ERRCODE_UNDEFINED_OBJECT),
                        errmsg_internal("cache lookup failed for relation %u",
                                        RelationGetRelid(relation)));
            relp = (Form_pg_class) GETSTRUCT(htup);
 
            /*
             * Copy tuple to relation->rd_rel. (See notes in
             * AllocateRelationDesc())
             */
            memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);
 
            /* Update rd_options while we have the tuple */
            if (relation->rd_options)
                pfree(relation->rd_options);
            RelationParseRelOptions(relation, htup);
 
            /*
             * Check the values in rd_att were set up correctly.  (We cannot
             * just copy them over now: formrdesc must have set up the rd_att
             * data correctly to start with, because it may already have been
             * copied into one or more catcache entries.)
             */
            Assert(relation->rd_att->tdtypeid == relp->reltype);
            Assert(relation->rd_att->tdtypmod == -1);
 
            ReleaseSysCache(htup);
 
            /* relowner had better be OK now, else we'll loop forever */
            if (relation->rd_rel->relowner == InvalidOid)
                elog(ERROR, "invalid relowner in pg_class entry for \"%s\"",
                     RelationGetRelationName(relation));
 
            restart = true;
        }
 
        /*
         * Fix data that isn't saved in relcache cache file.
         *
         * relhasrules or relhastriggers could possibly be wrong or out of
         * date.  If we don't actually find any rules or triggers, clear the
         * local copy of the flag so that we don't get into an infinite loop
         * here.  We don't make any attempt to fix the pg_class entry, though.
         */
        if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
        {
            RelationBuildRuleLock(relation);
            if (relation->rd_rules == NULL)
                relation->rd_rel->relhasrules = false;
            restart = true;
        }
        if (relation->rd_rel->relhastriggers && relation->trigdesc == NULL)
        {
            RelationBuildTriggers(relation);
            if (relation->trigdesc == NULL)
                relation->rd_rel->relhastriggers = false;
            restart = true;
        }
 
        /*
         * Re-load the row security policies if the relation has them, since
         * they are not preserved in the cache.  Note that we can never NOT
         * have a policy while relrowsecurity is true,
         * RelationBuildRowSecurity will create a single default-deny policy
         * if there is no policy defined in pg_policy.
         */
        if (relation->rd_rel->relrowsecurity && relation->rd_rsdesc == NULL)
        {
            RelationBuildRowSecurity(relation);
 
            Assert(relation->rd_rsdesc != NULL);
            restart = true;
        }
 
        /* Reload tableam data if needed */
        if (relation->rd_tableam == NULL &&
            (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind) || relation->rd_rel->relkind == RELKIND_SEQUENCE))
        {
            RelationInitTableAccessMethod(relation);
            Assert(relation->rd_tableam != NULL);
 
            restart = true;
        }
 
        /* Release hold on the relation */
        RelationDecrementReferenceCount(relation);
 
        /* Now, restart the hashtable scan if needed */
        if (restart)
        {
            hash_seq_term(&status);
            hash_seq_init(&status, RelationIdCache);
        }
    }
 
    /*
     * Lastly, write out new relcache cache files if needed.  We don't bother
     * to distinguish cases where only one of the two needs an update.
     */
    if (needNewCacheFile)
    {
        /*
         * Force all the catcaches to finish initializing and thereby open the
         * catalogs and indexes they use.  This will preload the relcache with
         * entries for all the most important system catalogs and indexes, so
         * that the init files will be most useful for future backends.
         */
        InitCatalogCachePhase2();
 
        /* now write the files */
        write_relcache_init_file(true);
        write_relcache_init_file(false);
    }
}
 
/*
 * Load one critical system index into the relcache
 *
 * indexoid is the OID of the target index, heapoid is the OID of the catalog
 * it belongs to.
 */
static void
load_critical_index(Oid indexoid, Oid heapoid)
{
    Relation    ird;
 
    /*
     * We must lock the underlying catalog before locking the index to avoid
     * deadlock, since RelationBuildDesc might well need to read the catalog,
     * and if anyone else is exclusive-locking this catalog and index they'll
     * be doing it in that order.
     */
    LockRelationOid(heapoid, AccessShareLock);
    LockRelationOid(indexoid, AccessShareLock);
    ird = RelationBuildDesc(indexoid, true);
    if (ird == NULL)
        ereport(PANIC,
                errcode(ERRCODE_DATA_CORRUPTED),
                errmsg_internal("could not open critical system index %u", indexoid));
    ird->rd_isnailed = true;
    ird->rd_refcnt = 1;
    UnlockRelationOid(indexoid, AccessShareLock);
    UnlockRelationOid(heapoid, AccessShareLock);
 
    (void) RelationGetIndexAttOptions(ird, false);
}
 
/*
 * GetPgClassDescriptor -- get a predefined tuple descriptor for pg_class
 * GetPgIndexDescriptor -- get a predefined tuple descriptor for pg_index
 *
 * We need this kluge because we have to be able to access non-fixed-width
 * fields of pg_class and pg_index before we have the standard catalog caches
 * available.  We use predefined data that's set up in just the same way as
 * the bootstrapped reldescs used by formrdesc().  The resulting tupdesc is
 * not 100% kosher: it does not have the correct rowtype OID in tdtypeid, nor
 * does it have a TupleConstr field.  But it's good enough for the purpose of
 * extracting fields.
 */
static TupleDesc
BuildHardcodedDescriptor(int natts, const FormData_pg_attribute *attrs)
{
    TupleDesc   result;
    MemoryContext oldcxt;
    int         i;
 
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 
    result = CreateTemplateTupleDesc(natts);
    result->tdtypeid = RECORDOID;   /* not right, but we don't care */
    result->tdtypmod = -1;
 
    for (i = 0; i < natts; i++)
    {
        memcpy(TupleDescAttr(result, i), &attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
 
        populate_compact_attribute(result, i);
    }
 
    /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
    TupleDescCompactAttr(result, 0)->attcacheoff = 0;
 
    /* Note: we don't bother to set up a TupleConstr entry */
 
    MemoryContextSwitchTo(oldcxt);
 
    return result;
}
 
static TupleDesc
GetPgClassDescriptor(void)
{
    static TupleDesc pgclassdesc = NULL;
 
    /* Already done? */
    if (pgclassdesc == NULL)
        pgclassdesc = BuildHardcodedDescriptor(Natts_pg_class,
                                               Desc_pg_class);
 
    return pgclassdesc;
}
 
static TupleDesc
GetPgIndexDescriptor(void)
{
    static TupleDesc pgindexdesc = NULL;
 
    /* Already done? */
    if (pgindexdesc == NULL)
        pgindexdesc = BuildHardcodedDescriptor(Natts_pg_index,
                                               Desc_pg_index);
 
    return pgindexdesc;
}
 
/*
 * Load any default attribute value definitions for the relation.
 *
 * ndef is the number of attributes that were marked atthasdef.
 *
 * Note: we don't make it a hard error to be missing some pg_attrdef records.
 * We can limp along as long as nothing needs to use the default value.  Code
 * that fails to find an expected AttrDefault record should throw an error.
 */
static void
AttrDefaultFetch(Relation relation, int ndef)
{
    AttrDefault *attrdef;
    Relation    adrel;
    SysScanDesc adscan;
    ScanKeyData skey;
    HeapTuple   htup;
    int         found = 0;
 
    /* Allocate array with room for as many entries as expected */
    attrdef = (AttrDefault *)
        MemoryContextAllocZero(CacheMemoryContext,
                               ndef * sizeof(AttrDefault));
 
    /* Search pg_attrdef for relevant entries */
    ScanKeyInit(&skey,
                Anum_pg_attrdef_adrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    adrel = table_open(AttrDefaultRelationId, AccessShareLock);
    adscan = systable_beginscan(adrel, AttrDefaultIndexId, true,
                                NULL, 1, &skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(adscan)))
    {
        Form_pg_attrdef adform = (Form_pg_attrdef) GETSTRUCT(htup);
        Datum       val;
        bool        isnull;
 
        /* protect limited size of array */
        if (found >= ndef)
        {
            elog(WARNING, "unexpected pg_attrdef record found for attribute %d of relation \"%s\"",
                 adform->adnum, RelationGetRelationName(relation));
            break;
        }
 
        val = fastgetattr(htup,
                          Anum_pg_attrdef_adbin,
                          adrel->rd_att, &isnull);
        if (isnull)
            elog(WARNING, "null adbin for attribute %d of relation \"%s\"",
                 adform->adnum, RelationGetRelationName(relation));
        else
        {
            /* detoast and convert to cstring in caller's context */
            char       *s = TextDatumGetCString(val);
 
            attrdef[found].adnum = adform->adnum;
            attrdef[found].adbin = MemoryContextStrdup(CacheMemoryContext, s);
            pfree(s);
            found++;
        }
    }
 
    systable_endscan(adscan);
    table_close(adrel, AccessShareLock);
 
    if (found != ndef)
        elog(WARNING, "%d pg_attrdef record(s) missing for relation \"%s\"",
             ndef - found, RelationGetRelationName(relation));
 
    /*
     * Sort the AttrDefault entries by adnum, for the convenience of
     * equalTupleDescs().  (Usually, they already will be in order, but this
     * might not be so if systable_getnext isn't using an index.)
     */
    if (found > 1)
        qsort(attrdef, found, sizeof(AttrDefault), AttrDefaultCmp);
 
    /* Install array only after it's fully valid */
    relation->rd_att->constr->defval = attrdef;
    relation->rd_att->constr->num_defval = found;
}
 
/*
 * qsort comparator to sort AttrDefault entries by adnum
 */
static int
AttrDefaultCmp(const void *a, const void *b)
{
    const AttrDefault *ada = (const AttrDefault *) a;
    const AttrDefault *adb = (const AttrDefault *) b;
 
    return pg_cmp_s16(ada->adnum, adb->adnum);
}
 
/*
 * Load any check constraints for the relation.
 *
 * As with defaults, if we don't find the expected number of them, just warn
 * here.  The executor should throw an error if an INSERT/UPDATE is attempted.
 */
static void
CheckConstraintFetch(Relation relation)
{
    ConstrCheck *check;
    int         ncheck = relation->rd_rel->relchecks;
    Relation    conrel;
    SysScanDesc conscan;
    ScanKeyData skey[1];
    HeapTuple   htup;
    int         found = 0;
 
    /* Allocate array with room for as many entries as expected */
    check = (ConstrCheck *)
        MemoryContextAllocZero(CacheMemoryContext,
                               ncheck * sizeof(ConstrCheck));
 
    /* Search pg_constraint for relevant entries */
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    conrel = table_open(ConstraintRelationId, AccessShareLock);
    conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
                                 NULL, 1, skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(conscan)))
    {
        Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);
        Datum       val;
        bool        isnull;
 
        /* We want check constraints only */
        if (conform->contype != CONSTRAINT_CHECK)
            continue;
 
        /* protect limited size of array */
        if (found >= ncheck)
        {
            elog(WARNING, "unexpected pg_constraint record found for relation \"%s\"",
                 RelationGetRelationName(relation));
            break;
        }
 
        check[found].ccenforced = conform->conenforced;
        check[found].ccvalid = conform->convalidated;
        check[found].ccnoinherit = conform->connoinherit;
        check[found].ccname = MemoryContextStrdup(CacheMemoryContext,
                                                  NameStr(conform->conname));
 
        /* Grab and test conbin is actually set */
        val = fastgetattr(htup,
                          Anum_pg_constraint_conbin,
                          conrel->rd_att, &isnull);
        if (isnull)
            elog(WARNING, "null conbin for relation \"%s\"",
                 RelationGetRelationName(relation));
        else
        {
            /* detoast and convert to cstring in caller's context */
            char       *s = TextDatumGetCString(val);
 
            check[found].ccbin = MemoryContextStrdup(CacheMemoryContext, s);
            pfree(s);
            found++;
        }
    }
 
    systable_endscan(conscan);
    table_close(conrel, AccessShareLock);
 
    if (found != ncheck)
        elog(WARNING, "%d pg_constraint record(s) missing for relation \"%s\"",
             ncheck - found, RelationGetRelationName(relation));
 
    /*
     * Sort the records by name.  This ensures that CHECKs are applied in a
     * deterministic order, and it also makes equalTupleDescs() faster.
     */
    if (found > 1)
        qsort(check, found, sizeof(ConstrCheck), CheckConstraintCmp);
 
    /* Install array only after it's fully valid */
    relation->rd_att->constr->check = check;
    relation->rd_att->constr->num_check = found;
}
 
/*
 * qsort comparator to sort ConstrCheck entries by name
 */
static int
CheckConstraintCmp(const void *a, const void *b)
{
    const ConstrCheck *ca = (const ConstrCheck *) a;
    const ConstrCheck *cb = (const ConstrCheck *) b;
 
    return strcmp(ca->ccname, cb->ccname);
}
 
/*
 * RelationGetFKeyList -- get a list of foreign key info for the relation
 *
 * Returns a list of ForeignKeyCacheInfo structs, one per FK constraining
 * the given relation.  This data is a direct copy of relevant fields from
 * pg_constraint.  The list items are in no particular order.
 *
 * CAUTION: the returned list is part of the relcache's data, and could
 * vanish in a relcache entry reset.  Callers must inspect or copy it
 * before doing anything that might trigger a cache flush, such as
 * system catalog accesses.  copyObject() can be used if desired.
 * (We define it this way because current callers want to filter and
 * modify the list entries anyway, so copying would be a waste of time.)
 */
List *
RelationGetFKeyList(Relation relation)
{
    List       *result;
    Relation    conrel;
    SysScanDesc conscan;
    ScanKeyData skey;
    HeapTuple   htup;
    List       *oldlist;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the list. */
    if (relation->rd_fkeyvalid)
        return relation->rd_fkeylist;
 
    /* Fast path: non-partitioned tables without triggers can't have FKs */
    if (!relation->rd_rel->relhastriggers &&
        relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
        return NIL;
 
    /*
     * We build the list we intend to return (in the caller's context) while
     * doing the scan.  After successfully completing the scan, we copy that
     * list into the relcache entry.  This avoids cache-context memory leakage
     * if we get some sort of error partway through.
     */
    result = NIL;
 
    /* Prepare to scan pg_constraint for entries having conrelid = this rel. */
    ScanKeyInit(&skey,
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    conrel = table_open(ConstraintRelationId, AccessShareLock);
    conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
                                 NULL, 1, &skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(conscan)))
    {
        Form_pg_constraint constraint = (Form_pg_constraint) GETSTRUCT(htup);
        ForeignKeyCacheInfo *info;
 
        /* consider only foreign keys */
        if (constraint->contype != CONSTRAINT_FOREIGN)
            continue;
 
        info = makeNode(ForeignKeyCacheInfo);
        info->conoid = constraint->oid;
        info->conrelid = constraint->conrelid;
        info->confrelid = constraint->confrelid;
 
        DeconstructFkConstraintRow(htup, &info->nkeys,
                                   info->conkey,
                                   info->confkey,
                                   info->conpfeqop,
                                   NULL, NULL, NULL, NULL);
 
        /* Add FK's node to the result list */
        result = lappend(result, info);
    }
 
    systable_endscan(conscan);
    table_close(conrel, AccessShareLock);
 
    /* Now save a copy of the completed list in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    oldlist = relation->rd_fkeylist;
    relation->rd_fkeylist = copyObject(result);
    relation->rd_fkeyvalid = true;
    MemoryContextSwitchTo(oldcxt);
 
    /* Don't leak the old list, if there is one */
    list_free_deep(oldlist);
 
    return result;
}
 
/*
 * RelationGetIndexList -- get a list of OIDs of indexes on this relation
 *
 * The index list is created only if someone requests it.  We scan pg_index
 * to find relevant indexes, and add the list to the relcache entry so that
 * we won't have to compute it again.  Note that shared cache inval of a
 * relcache entry will delete the old list and set rd_indexvalid to false,
 * so that we must recompute the index list on next request.  This handles
 * creation or deletion of an index.
 *
 * Indexes that are marked not indislive are omitted from the returned list.
 * Such indexes are expected to be dropped momentarily, and should not be
 * touched at all by any caller of this function.
 *
 * The returned list is guaranteed to be sorted in order by OID.  This is
 * needed by the executor, since for index types that we obtain exclusive
 * locks on when updating the index, all backends must lock the indexes in
 * the same order or we will get deadlocks (see ExecOpenIndices()).  Any
 * consistent ordering would do, but ordering by OID is easy.
 *
 * Since shared cache inval causes the relcache's copy of the list to go away,
 * we return a copy of the list palloc'd in the caller's context.  The caller
 * may list_free() the returned list after scanning it. This is necessary
 * since the caller will typically be doing syscache lookups on the relevant
 * indexes, and syscache lookup could cause SI messages to be processed!
 *
 * In exactly the same way, we update rd_pkindex, which is the OID of the
 * relation's primary key index if any, else InvalidOid; and rd_replidindex,
 * which is the pg_class OID of an index to be used as the relation's
 * replication identity index, or InvalidOid if there is no such index.
 */
List *
RelationGetIndexList(Relation relation)
{
    Relation    indrel;
    SysScanDesc indscan;
    ScanKeyData skey;
    HeapTuple   htup;
    List       *result;
    List       *oldlist;
    char        replident = relation->rd_rel->relreplident;
    Oid         pkeyIndex = InvalidOid;
    Oid         candidateIndex = InvalidOid;
    bool        pkdeferrable = false;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the list. */
    if (relation->rd_indexvalid)
        return list_copy(relation->rd_indexlist);
 
    /*
     * We build the list we intend to return (in the caller's context) while
     * doing the scan.  After successfully completing the scan, we copy that
     * list into the relcache entry.  This avoids cache-context memory leakage
     * if we get some sort of error partway through.
     */
    result = NIL;
 
    /* Prepare to scan pg_index for entries having indrelid = this rel. */
    ScanKeyInit(&skey,
                Anum_pg_index_indrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    indrel = table_open(IndexRelationId, AccessShareLock);
    indscan = systable_beginscan(indrel, IndexIndrelidIndexId, true,
                                 NULL, 1, &skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(indscan)))
    {
        Form_pg_index index = (Form_pg_index) GETSTRUCT(htup);
 
        /*
         * Ignore any indexes that are currently being dropped.  This will
         * prevent them from being searched, inserted into, or considered in
         * HOT-safety decisions.  It's unsafe to touch such an index at all
         * since its catalog entries could disappear at any instant.
         */
        if (!index->indislive)
            continue;
 
        /* add index's OID to result list */
        result = lappend_oid(result, index->indexrelid);
 
        /*
         * Non-unique or predicate indexes aren't interesting for either oid
         * indexes or replication identity indexes, so don't check them.
         * Deferred ones are not useful for replication identity either; but
         * we do include them if they are PKs.
         */
        if (!index->indisunique ||
            !heap_attisnull(htup, Anum_pg_index_indpred, NULL))
            continue;
 
        /*
         * Remember primary key index, if any.  For regular tables we do this
         * only if the index is valid; but for partitioned tables, then we do
         * it even if it's invalid.
         *
         * The reason for returning invalid primary keys for partitioned
         * tables is that we need it to prevent drop of not-null constraints
         * that may underlie such a primary key, which is only a problem for
         * partitioned tables.
         */
        if (index->indisprimary &&
            (index->indisvalid ||
             relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE))
        {
            pkeyIndex = index->indexrelid;
            pkdeferrable = !index->indimmediate;
        }
 
        if (!index->indimmediate)
            continue;
 
        if (!index->indisvalid)
            continue;
 
        /* remember explicitly chosen replica index */
        if (index->indisreplident)
            candidateIndex = index->indexrelid;
    }
 
    systable_endscan(indscan);
 
    table_close(indrel, AccessShareLock);
 
    /* Sort the result list into OID order, per API spec. */
    list_sort(result, list_oid_cmp);
 
    /* Now save a copy of the completed list in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    oldlist = relation->rd_indexlist;
    relation->rd_indexlist = list_copy(result);
    relation->rd_pkindex = pkeyIndex;
    relation->rd_ispkdeferrable = pkdeferrable;
    if (replident == REPLICA_IDENTITY_DEFAULT && OidIsValid(pkeyIndex) && !pkdeferrable)
        relation->rd_replidindex = pkeyIndex;
    else if (replident == REPLICA_IDENTITY_INDEX && OidIsValid(candidateIndex))
        relation->rd_replidindex = candidateIndex;
    else
        relation->rd_replidindex = InvalidOid;
    relation->rd_indexvalid = true;
    MemoryContextSwitchTo(oldcxt);
 
    /* Don't leak the old list, if there is one */
    list_free(oldlist);
 
    return result;
}
 
/*
 * RelationGetStatExtList
 *      get a list of OIDs of statistics objects on this relation
 *
 * The statistics list is created only if someone requests it, in a way
 * similar to RelationGetIndexList().  We scan pg_statistic_ext to find
 * relevant statistics, and add the list to the relcache entry so that we
 * won't have to compute it again.  Note that shared cache inval of a
 * relcache entry will delete the old list and set rd_statvalid to 0,
 * so that we must recompute the statistics list on next request.  This
 * handles creation or deletion of a statistics object.
 *
 * The returned list is guaranteed to be sorted in order by OID, although
 * this is not currently needed.
 *
 * Since shared cache inval causes the relcache's copy of the list to go away,
 * we return a copy of the list palloc'd in the caller's context.  The caller
 * may list_free() the returned list after scanning it. This is necessary
 * since the caller will typically be doing syscache lookups on the relevant
 * statistics, and syscache lookup could cause SI messages to be processed!
 */
List *
RelationGetStatExtList(Relation relation)
{
    Relation    indrel;
    SysScanDesc indscan;
    ScanKeyData skey;
    HeapTuple   htup;
    List       *result;
    List       *oldlist;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the list. */
    if (relation->rd_statvalid != 0)
        return list_copy(relation->rd_statlist);
 
    /*
     * We build the list we intend to return (in the caller's context) while
     * doing the scan.  After successfully completing the scan, we copy that
     * list into the relcache entry.  This avoids cache-context memory leakage
     * if we get some sort of error partway through.
     */
    result = NIL;
 
    /*
     * Prepare to scan pg_statistic_ext for entries having stxrelid = this
     * rel.
     */
    ScanKeyInit(&skey,
                Anum_pg_statistic_ext_stxrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
 
    indrel = table_open(StatisticExtRelationId, AccessShareLock);
    indscan = systable_beginscan(indrel, StatisticExtRelidIndexId, true,
                                 NULL, 1, &skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(indscan)))
    {
        Oid         oid = ((Form_pg_statistic_ext) GETSTRUCT(htup))->oid;
 
        result = lappend_oid(result, oid);
    }
 
    systable_endscan(indscan);
 
    table_close(indrel, AccessShareLock);
 
    /* Sort the result list into OID order, per API spec. */
    list_sort(result, list_oid_cmp);
 
    /* Now save a copy of the completed list in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    oldlist = relation->rd_statlist;
    relation->rd_statlist = list_copy(result);
 
    relation->rd_statvalid = true;
    MemoryContextSwitchTo(oldcxt);
 
    /* Don't leak the old list, if there is one */
    list_free(oldlist);
 
    return result;
}
 
/*
 * RelationGetPrimaryKeyIndex -- get OID of the relation's primary key index
 *
 * Returns InvalidOid if there is no such index, or if the primary key is
 * DEFERRABLE and the caller isn't OK with that.
 */
Oid
RelationGetPrimaryKeyIndex(Relation relation, bool deferrable_ok)
{
    List       *ilist;
 
    if (!relation->rd_indexvalid)
    {
        /* RelationGetIndexList does the heavy lifting. */
        ilist = RelationGetIndexList(relation);
        list_free(ilist);
        Assert(relation->rd_indexvalid);
    }
 
    if (deferrable_ok)
        return relation->rd_pkindex;
    else if (relation->rd_ispkdeferrable)
        return InvalidOid;
    return relation->rd_pkindex;
}
 
/*
 * RelationGetReplicaIndex -- get OID of the relation's replica identity index
 *
 * Returns InvalidOid if there is no such index.
 */
Oid
RelationGetReplicaIndex(Relation relation)
{
    List       *ilist;
 
    if (!relation->rd_indexvalid)
    {
        /* RelationGetIndexList does the heavy lifting. */
        ilist = RelationGetIndexList(relation);
        list_free(ilist);
        Assert(relation->rd_indexvalid);
    }
 
    return relation->rd_replidindex;
}
 
/*
 * RelationGetIndexExpressions -- get the index expressions for an index
 *
 * We cache the result of transforming pg_index.indexprs into a node tree.
 * If the rel is not an index or has no expressional columns, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexExpressions(Relation relation)
{
    List       *result;
    Datum       exprsDatum;
    bool        isnull;
    char       *exprsString;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the result. */
    if (relation->rd_indexprs)
        return copyObject(relation->rd_indexprs);
 
    /* Quick exit if there is nothing to do. */
    if (relation->rd_indextuple == NULL ||
        heap_attisnull(relation->rd_indextuple, Anum_pg_index_indexprs, NULL))
        return NIL;
 
    /*
     * We build the tree we intend to return in the caller's context. After
     * successfully completing the work, we copy it into the relcache entry.
     * This avoids problems if we get some sort of error partway through.
     */
    exprsDatum = heap_getattr(relation->rd_indextuple,
                              Anum_pg_index_indexprs,
                              GetPgIndexDescriptor(),
                              &isnull);
    Assert(!isnull);
    exprsString = TextDatumGetCString(exprsDatum);
    result = (List *) stringToNode(exprsString);
    pfree(exprsString);
 
    /*
     * Run the expressions through eval_const_expressions. This is not just an
     * optimization, but is necessary, because the planner will be comparing
     * them to similarly-processed qual clauses, and may fail to detect valid
     * matches without this.  We must not use canonicalize_qual, however,
     * since these aren't qual expressions.
     */
    result = (List *) eval_const_expressions(NULL, (Node *) result);
 
    /* May as well fix opfuncids too */
    fix_opfuncids((Node *) result);
 
    /* Now save a copy of the completed tree in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
    relation->rd_indexprs = copyObject(result);
    MemoryContextSwitchTo(oldcxt);
 
    return result;
}
 
/*
 * RelationGetDummyIndexExpressions -- get dummy expressions for an index
 *
 * Return a list of dummy expressions (just Const nodes) with the same
 * types/typmods/collations as the index's real expressions.  This is
 * useful in situations where we don't want to run any user-defined code.
 */
List *
RelationGetDummyIndexExpressions(Relation relation)
{
    List       *result;
    Datum       exprsDatum;
    bool        isnull;
    char       *exprsString;
    List       *rawExprs;
    ListCell   *lc;
 
    /* Quick exit if there is nothing to do. */
    if (relation->rd_indextuple == NULL ||
        heap_attisnull(relation->rd_indextuple, Anum_pg_index_indexprs, NULL))
        return NIL;
 
    /* Extract raw node tree(s) from index tuple. */
    exprsDatum = heap_getattr(relation->rd_indextuple,
                              Anum_pg_index_indexprs,
                              GetPgIndexDescriptor(),
                              &isnull);
    Assert(!isnull);
    exprsString = TextDatumGetCString(exprsDatum);
    rawExprs = (List *) stringToNode(exprsString);
    pfree(exprsString);
 
    /* Construct null Consts; the typlen and typbyval are arbitrary. */
    result = NIL;
    foreach(lc, rawExprs)
    {
        Node       *rawExpr = (Node *) lfirst(lc);
 
        result = lappend(result,
                         makeConst(exprType(rawExpr),
                                   exprTypmod(rawExpr),
                                   exprCollation(rawExpr),
                                   1,
                                   (Datum) 0,
                                   true,
                                   true));
    }
 
    return result;
}
 
/*
 * RelationGetIndexPredicate -- get the index predicate for an index
 *
 * We cache the result of transforming pg_index.indpred into an implicit-AND
 * node tree (suitable for use in planning).
 * If the rel is not an index or has no predicate, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexPredicate(Relation relation)
{
    List       *result;
    Datum       predDatum;
    bool        isnull;
    char       *predString;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the result. */
    if (relation->rd_indpred)
        return copyObject(relation->rd_indpred);
 
    /* Quick exit if there is nothing to do. */
    if (relation->rd_indextuple == NULL ||
        heap_attisnull(relation->rd_indextuple, Anum_pg_index_indpred, NULL))
        return NIL;
 
    /*
     * We build the tree we intend to return in the caller's context. After
     * successfully completing the work, we copy it into the relcache entry.
     * This avoids problems if we get some sort of error partway through.
     */
    predDatum = heap_getattr(relation->rd_indextuple,
                             Anum_pg_index_indpred,
                             GetPgIndexDescriptor(),
                             &isnull);
    Assert(!isnull);
    predString = TextDatumGetCString(predDatum);
    result = (List *) stringToNode(predString);
    pfree(predString);
 
    /*
     * Run the expression through const-simplification and canonicalization.
     * This is not just an optimization, but is necessary, because the planner
     * will be comparing it to similarly-processed qual clauses, and may fail
     * to detect valid matches without this.  This must match the processing
     * done to qual clauses in preprocess_expression()!  (We can skip the
     * stuff involving subqueries, however, since we don't allow any in index
     * predicates.)
     */
    result = (List *) eval_const_expressions(NULL, (Node *) result);
 
    result = (List *) canonicalize_qual((Expr *) result, false);
 
    /* Also convert to implicit-AND format */
    result = make_ands_implicit((Expr *) result);
 
    /* May as well fix opfuncids too */
    fix_opfuncids((Node *) result);
 
    /* Now save a copy of the completed tree in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
    relation->rd_indpred = copyObject(result);
    MemoryContextSwitchTo(oldcxt);
 
    return result;
}
 
/*
 * RelationGetIndexAttrBitmap -- get a bitmap of index attribute numbers
 *
 * The result has a bit set for each attribute used anywhere in the index
 * definitions of all the indexes on this relation.  (This includes not only
 * simple index keys, but attributes used in expressions and partial-index
 * predicates.)
 *
 * Depending on attrKind, a bitmap covering attnums for certain columns is
 * returned:
 *  INDEX_ATTR_BITMAP_KEY           Columns in non-partial unique indexes not
 *                                  in expressions (i.e., usable for FKs)
 *  INDEX_ATTR_BITMAP_PRIMARY_KEY   Columns in the table's primary key
 *                                  (beware: even if PK is deferrable!)
 *  INDEX_ATTR_BITMAP_IDENTITY_KEY  Columns in the table's replica identity
 *                                  index (empty if FULL)
 *  INDEX_ATTR_BITMAP_HOT_BLOCKING  Columns that block updates from being HOT
 *  INDEX_ATTR_BITMAP_SUMMARIZED    Columns included in summarizing indexes
 *
 * Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
 * we can include system attributes (e.g., OID) in the bitmap representation.
 *
 * Deferred indexes are considered for the primary key, but not for replica
 * identity.
 *
 * Caller had better hold at least RowExclusiveLock on the target relation
 * to ensure it is safe (deadlock-free) for us to take locks on the relation's
 * indexes.  Note that since the introduction of CREATE INDEX CONCURRENTLY,
 * that lock level doesn't guarantee a stable set of indexes, so we have to
 * be prepared to retry here in case of a change in the set of indexes.
 *
 * The returned result is palloc'd in the caller's memory context and should
 * be bms_free'd when not needed anymore.
 */
Bitmapset *
RelationGetIndexAttrBitmap(Relation relation, IndexAttrBitmapKind attrKind)
{
    Bitmapset  *uindexattrs;    /* columns in unique indexes */
    Bitmapset  *pkindexattrs;   /* columns in the primary index */
    Bitmapset  *idindexattrs;   /* columns in the replica identity */
    Bitmapset  *hotblockingattrs;   /* columns with HOT blocking indexes */
    Bitmapset  *summarizedattrs;    /* columns with summarizing indexes */
    List       *indexoidlist;
    List       *newindexoidlist;
    Oid         relpkindex;
    Oid         relreplindex;
    ListCell   *l;
    MemoryContext oldcxt;
 
    /* Quick exit if we already computed the result. */
    if (relation->rd_attrsvalid)
    {
        switch (attrKind)
        {
            case INDEX_ATTR_BITMAP_KEY:
                return bms_copy(relation->rd_keyattr);
            case INDEX_ATTR_BITMAP_PRIMARY_KEY:
                return bms_copy(relation->rd_pkattr);
            case INDEX_ATTR_BITMAP_IDENTITY_KEY:
                return bms_copy(relation->rd_idattr);
            case INDEX_ATTR_BITMAP_HOT_BLOCKING:
                return bms_copy(relation->rd_hotblockingattr);
            case INDEX_ATTR_BITMAP_SUMMARIZED:
                return bms_copy(relation->rd_summarizedattr);
            default:
                elog(ERROR, "unknown attrKind %u", attrKind);
        }
    }
 
    /* Fast path if definitely no indexes */
    if (!RelationGetForm(relation)->relhasindex)
        return NULL;
 
    /*
     * Get cached list of index OIDs. If we have to start over, we do so here.
     */
restart:
    indexoidlist = RelationGetIndexList(relation);
 
    /* Fall out if no indexes (but relhasindex was set) */
    if (indexoidlist == NIL)
        return NULL;
 
    /*
     * Copy the rd_pkindex and rd_replidindex values computed by
     * RelationGetIndexList before proceeding.  This is needed because a
     * relcache flush could occur inside index_open below, resetting the
     * fields managed by RelationGetIndexList.  We need to do the work with
     * stable values of these fields.
     */
    relpkindex = relation->rd_pkindex;
    relreplindex = relation->rd_replidindex;
 
    /*
     * For each index, add referenced attributes to indexattrs.
     *
     * Note: we consider all indexes returned by RelationGetIndexList, even if
     * they are not indisready or indisvalid.  This is important because an
     * index for which CREATE INDEX CONCURRENTLY has just started must be
     * included in HOT-safety decisions (see README.HOT).  If a DROP INDEX
     * CONCURRENTLY is far enough along that we should ignore the index, it
     * won't be returned at all by RelationGetIndexList.
     */
    uindexattrs = NULL;
    pkindexattrs = NULL;
    idindexattrs = NULL;
    hotblockingattrs = NULL;
    summarizedattrs = NULL;
    foreach(l, indexoidlist)
    {
        Oid         indexOid = lfirst_oid(l);
        Relation    indexDesc;
        Datum       datum;
        bool        isnull;
        Node       *indexExpressions;
        Node       *indexPredicate;
        int         i;
        bool        isKey;      /* candidate key */
        bool        isPK;       /* primary key */
        bool        isIDKey;    /* replica identity index */
        Bitmapset **attrs;
 
        indexDesc = index_open(indexOid, AccessShareLock);
 
        /*
         * Extract index expressions and index predicate.  Note: Don't use
         * RelationGetIndexExpressions()/RelationGetIndexPredicate(), because
         * those might run constant expressions evaluation, which needs a
         * snapshot, which we might not have here.  (Also, it's probably more
         * sound to collect the bitmaps before any transformations that might
         * eliminate columns, but the practical impact of this is limited.)
         */
 
        datum = heap_getattr(indexDesc->rd_indextuple, Anum_pg_index_indexprs,
                             GetPgIndexDescriptor(), &isnull);
        if (!isnull)
            indexExpressions = stringToNode(TextDatumGetCString(datum));
        else
            indexExpressions = NULL;
 
        datum = heap_getattr(indexDesc->rd_indextuple, Anum_pg_index_indpred,
                             GetPgIndexDescriptor(), &isnull);
        if (!isnull)
            indexPredicate = stringToNode(TextDatumGetCString(datum));
        else
            indexPredicate = NULL;
 
        /* Can this index be referenced by a foreign key? */
        isKey = indexDesc->rd_index->indisunique &&
            indexExpressions == NULL &&
            indexPredicate == NULL;
 
        /* Is this a primary key? */
        isPK = (indexOid == relpkindex);
 
        /* Is this index the configured (or default) replica identity? */
        isIDKey = (indexOid == relreplindex);
 
        /*
         * If the index is summarizing, it doesn't block HOT updates, but we
         * may still need to update it (if the attributes were modified). So
         * decide which bitmap we'll update in the following loop.
         */
        if (indexDesc->rd_indam->amsummarizing)
            attrs = &summarizedattrs;
        else
            attrs = &hotblockingattrs;
 
        /* Collect simple attribute references */
        for (i = 0; i < indexDesc->rd_index->indnatts; i++)
        {
            int         attrnum = indexDesc->rd_index->indkey.values[i];
 
            /*
             * Since we have covering indexes with non-key columns, we must
             * handle them accurately here. non-key columns must be added into
             * hotblockingattrs or summarizedattrs, since they are in index,
             * and update shouldn't miss them.
             *
             * Summarizing indexes do not block HOT, but do need to be updated
             * when the column value changes, thus require a separate
             * attribute bitmapset.
             *
             * Obviously, non-key columns couldn't be referenced by foreign
             * key or identity key. Hence we do not include them into
             * uindexattrs, pkindexattrs and idindexattrs bitmaps.
             */
            if (attrnum != 0)
            {
                *attrs = bms_add_member(*attrs,
                                        attrnum - FirstLowInvalidHeapAttributeNumber);
 
                if (isKey && i < indexDesc->rd_index->indnkeyatts)
                    uindexattrs = bms_add_member(uindexattrs,
                                                 attrnum - FirstLowInvalidHeapAttributeNumber);
 
                if (isPK && i < indexDesc->rd_index->indnkeyatts)
                    pkindexattrs = bms_add_member(pkindexattrs,
                                                  attrnum - FirstLowInvalidHeapAttributeNumber);
 
                if (isIDKey && i < indexDesc->rd_index->indnkeyatts)
                    idindexattrs = bms_add_member(idindexattrs,
                                                  attrnum - FirstLowInvalidHeapAttributeNumber);
            }
        }
 
        /* Collect all attributes used in expressions, too */
        pull_varattnos(indexExpressions, 1, attrs);
 
        /* Collect all attributes in the index predicate, too */
        pull_varattnos(indexPredicate, 1, attrs);
 
        index_close(indexDesc, AccessShareLock);
    }
 
    /*
     * During one of the index_opens in the above loop, we might have received
     * a relcache flush event on this relcache entry, which might have been
     * signaling a change in the rel's index list.  If so, we'd better start
     * over to ensure we deliver up-to-date attribute bitmaps.
     */
    newindexoidlist = RelationGetIndexList(relation);
    if (equal(indexoidlist, newindexoidlist) &&
        relpkindex == relation->rd_pkindex &&
        relreplindex == relation->rd_replidindex)
    {
        /* Still the same index set, so proceed */
        list_free(newindexoidlist);
        list_free(indexoidlist);
    }
    else
    {
        /* Gotta do it over ... might as well not leak memory */
        list_free(newindexoidlist);
        list_free(indexoidlist);
        bms_free(uindexattrs);
        bms_free(pkindexattrs);
        bms_free(idindexattrs);
        bms_free(hotblockingattrs);
        bms_free(summarizedattrs);
 
        goto restart;
    }
 
    /* Don't leak the old values of these bitmaps, if any */
    relation->rd_attrsvalid = false;
    bms_free(relation->rd_keyattr);
    relation->rd_keyattr = NULL;
    bms_free(relation->rd_pkattr);
    relation->rd_pkattr = NULL;
    bms_free(relation->rd_idattr);
    relation->rd_idattr = NULL;
    bms_free(relation->rd_hotblockingattr);
    relation->rd_hotblockingattr = NULL;
    bms_free(relation->rd_summarizedattr);
    relation->rd_summarizedattr = NULL;
 
    /*
     * Now save copies of the bitmaps in the relcache entry.  We intentionally
     * set rd_attrsvalid last, because that's the one that signals validity of
     * the values; if we run out of memory before making that copy, we won't
     * leave the relcache entry looking like the other ones are valid but
     * empty.
     */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    relation->rd_keyattr = bms_copy(uindexattrs);
    relation->rd_pkattr = bms_copy(pkindexattrs);
    relation->rd_idattr = bms_copy(idindexattrs);
    relation->rd_hotblockingattr = bms_copy(hotblockingattrs);
    relation->rd_summarizedattr = bms_copy(summarizedattrs);
    relation->rd_attrsvalid = true;
    MemoryContextSwitchTo(oldcxt);
 
    /* We return our original working copy for caller to play with */
    switch (attrKind)
    {
        case INDEX_ATTR_BITMAP_KEY:
            return uindexattrs;
        case INDEX_ATTR_BITMAP_PRIMARY_KEY:
            return pkindexattrs;
        case INDEX_ATTR_BITMAP_IDENTITY_KEY:
            return idindexattrs;
        case INDEX_ATTR_BITMAP_HOT_BLOCKING:
            return hotblockingattrs;
        case INDEX_ATTR_BITMAP_SUMMARIZED:
            return summarizedattrs;
        default:
            elog(ERROR, "unknown attrKind %u", attrKind);
            return NULL;
    }
}
 
/*
 * RelationGetIdentityKeyBitmap -- get a bitmap of replica identity