indexcmds.c

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/*-------------------------------------------------------------------------
 *
 * indexcmds.c
 *    POSTGRES define and remove index code.
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/commands/indexcmds.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/amapi.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/pg_am.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "commands/comment.h"
#include "commands/dbcommands.h"
#include "commands/defrem.h"
#include "commands/event_trigger.h"
#include "commands/progress.h"
#include "commands/tablecmds.h"
#include "commands/tablespace.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "parser/parse_coerce.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "partitioning/partdesc.h"
#include "pgstat.h"
#include "rewrite/rewriteManip.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/sinvaladt.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/partcache.h"
#include "utils/pg_rusage.h"
#include "utils/regproc.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"


/* non-export function prototypes */
static void CheckPredicate(Expr *predicate);
static void ComputeIndexAttrs(IndexInfo *indexInfo,
                              Oid *typeOidP,
                              Oid *collationOidP,
                              Oid *classOidP,
                              int16 *colOptionP,
                              List *attList,
                              List *exclusionOpNames,
                              Oid relId,
                              const char *accessMethodName, Oid accessMethodId,
                              bool amcanorder,
                              bool isconstraint);
static char *ChooseIndexName(const char *tabname, Oid namespaceId,
                             List *colnames, List *exclusionOpNames,
                             bool primary, bool isconstraint);
static char *ChooseIndexNameAddition(List *colnames);
static List *ChooseIndexColumnNames(List *indexElems);
static void RangeVarCallbackForReindexIndex(const RangeVar *relation,
                                            Oid relId, Oid oldRelId, void *arg);
static bool ReindexRelationConcurrently(Oid relationOid, int options);
static void ReindexPartitionedIndex(Relation parentIdx);
static void update_relispartition(Oid relationId, bool newval);

/*
 * callback argument type for RangeVarCallbackForReindexIndex()
 */
struct ReindexIndexCallbackState
{
    bool        concurrent;     /* flag from statement */
    Oid         locked_table_oid;   /* tracks previously locked table */
};

/*
 * CheckIndexCompatible
 *      Determine whether an existing index definition is compatible with a
 *      prospective index definition, such that the existing index storage
 *      could become the storage of the new index, avoiding a rebuild.
 *
 * 'heapRelation': the relation the index would apply to.
 * 'accessMethodName': name of the AM to use.
 * 'attributeList': a list of IndexElem specifying columns and expressions
 *      to index on.
 * 'exclusionOpNames': list of names of exclusion-constraint operators,
 *      or NIL if not an exclusion constraint.
 *
 * This is tailored to the needs of ALTER TABLE ALTER TYPE, which recreates
 * any indexes that depended on a changing column from their pg_get_indexdef
 * or pg_get_constraintdef definitions.  We omit some of the sanity checks of
 * DefineIndex.  We assume that the old and new indexes have the same number
 * of columns and that if one has an expression column or predicate, both do.
 * Errors arising from the attribute list still apply.
 *
 * Most column type changes that can skip a table rewrite do not invalidate
 * indexes.  We acknowledge this when all operator classes, collations and
 * exclusion operators match.  Though we could further permit intra-opfamily
 * changes for btree and hash indexes, that adds subtle complexity with no
 * concrete benefit for core types. Note, that INCLUDE columns aren't
 * checked by this function, for them it's enough that table rewrite is
 * skipped.
 *
 * When a comparison or exclusion operator has a polymorphic input type, the
 * actual input types must also match.  This defends against the possibility
 * that operators could vary behavior in response to get_fn_expr_argtype().
 * At present, this hazard is theoretical: check_exclusion_constraint() and
 * all core index access methods decline to set fn_expr for such calls.
 *
 * We do not yet implement a test to verify compatibility of expression
 * columns or predicates, so assume any such index is incompatible.
 */
bool
CheckIndexCompatible(Oid oldId,
                     const char *accessMethodName,
                     List *attributeList,
                     List *exclusionOpNames)
{
    bool        isconstraint;
    Oid        *typeObjectId;
    Oid        *collationObjectId;
    Oid        *classObjectId;
    Oid         accessMethodId;
    Oid         relationId;
    HeapTuple   tuple;
    Form_pg_index indexForm;
    Form_pg_am  accessMethodForm;
    IndexAmRoutine *amRoutine;
    bool        amcanorder;
    int16      *coloptions;
    IndexInfo  *indexInfo;
    int         numberOfAttributes;
    int         old_natts;
    bool        isnull;
    bool        ret = true;
    oidvector  *old_indclass;
    oidvector  *old_indcollation;
    Relation    irel;
    int         i;
    Datum       d;

    /* Caller should already have the relation locked in some way. */
    relationId = IndexGetRelation(oldId, false);

    /*
     * We can pretend isconstraint = false unconditionally.  It only serves to
     * decide the text of an error message that should never happen for us.
     */
    isconstraint = false;

    numberOfAttributes = list_length(attributeList);
    Assert(numberOfAttributes > 0);
    Assert(numberOfAttributes <= INDEX_MAX_KEYS);

    /* look up the access method */
    tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
    if (!HeapTupleIsValid(tuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("access method \"%s\" does not exist",
                        accessMethodName)));
    accessMethodForm = (Form_pg_am) GETSTRUCT(tuple);
    accessMethodId = accessMethodForm->oid;
    amRoutine = GetIndexAmRoutine(accessMethodForm->amhandler);
    ReleaseSysCache(tuple);

    amcanorder = amRoutine->amcanorder;

    /*
     * Compute the operator classes, collations, and exclusion operators for
     * the new index, so we can test whether it's compatible with the existing
     * one.  Note that ComputeIndexAttrs might fail here, but that's OK:
     * DefineIndex would have called this function with the same arguments
     * later on, and it would have failed then anyway.  Our attributeList
     * contains only key attributes, thus we're filling ii_NumIndexAttrs and
     * ii_NumIndexKeyAttrs with same value.
     */
    indexInfo = makeIndexInfo(numberOfAttributes, numberOfAttributes,
                              accessMethodId, NIL, NIL, false, false, false);
    typeObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    collationObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    classObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    coloptions = (int16 *) palloc(numberOfAttributes * sizeof(int16));
    ComputeIndexAttrs(indexInfo,
                      typeObjectId, collationObjectId, classObjectId,
                      coloptions, attributeList,
                      exclusionOpNames, relationId,
                      accessMethodName, accessMethodId,
                      amcanorder, isconstraint);


    /* Get the soon-obsolete pg_index tuple. */
    tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(oldId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for index %u", oldId);
    indexForm = (Form_pg_index) GETSTRUCT(tuple);

    /*
     * We don't assess expressions or predicates; assume incompatibility.
     * Also, if the index is invalid for any reason, treat it as incompatible.
     */
    if (!(heap_attisnull(tuple, Anum_pg_index_indpred, NULL) &&
          heap_attisnull(tuple, Anum_pg_index_indexprs, NULL) &&
          indexForm->indisvalid))
    {
        ReleaseSysCache(tuple);
        return false;
    }

    /* Any change in operator class or collation breaks compatibility. */
    old_natts = indexForm->indnkeyatts;
    Assert(old_natts == numberOfAttributes);

    d = SysCacheGetAttr(INDEXRELID, tuple, Anum_pg_index_indcollation, &isnull);
    Assert(!isnull);
    old_indcollation = (oidvector *) DatumGetPointer(d);

    d = SysCacheGetAttr(INDEXRELID, tuple, Anum_pg_index_indclass, &isnull);
    Assert(!isnull);
    old_indclass = (oidvector *) DatumGetPointer(d);

    ret = (memcmp(old_indclass->values, classObjectId,
                  old_natts * sizeof(Oid)) == 0 &&
           memcmp(old_indcollation->values, collationObjectId,
                  old_natts * sizeof(Oid)) == 0);

    ReleaseSysCache(tuple);

    if (!ret)
        return false;

    /* For polymorphic opcintype, column type changes break compatibility. */
    irel = index_open(oldId, AccessShareLock);  /* caller probably has a lock */
    for (i = 0; i < old_natts; i++)
    {
        if (IsPolymorphicType(get_opclass_input_type(classObjectId[i])) &&
            TupleDescAttr(irel->rd_att, i)->atttypid != typeObjectId[i])
        {
            ret = false;
            break;
        }
    }

    /* Any change in exclusion operator selections breaks compatibility. */
    if (ret && indexInfo->ii_ExclusionOps != NULL)
    {
        Oid        *old_operators,
                   *old_procs;
        uint16     *old_strats;

        RelationGetExclusionInfo(irel, &old_operators, &old_procs, &old_strats);
        ret = memcmp(old_operators, indexInfo->ii_ExclusionOps,
                     old_natts * sizeof(Oid)) == 0;

        /* Require an exact input type match for polymorphic operators. */
        if (ret)
        {
            for (i = 0; i < old_natts && ret; i++)
            {
                Oid         left,
                            right;

                op_input_types(indexInfo->ii_ExclusionOps[i], &left, &right);
                if ((IsPolymorphicType(left) || IsPolymorphicType(right)) &&
                    TupleDescAttr(irel->rd_att, i)->atttypid != typeObjectId[i])
                {
                    ret = false;
                    break;
                }
            }
        }
    }

    index_close(irel, NoLock);
    return ret;
}


/*
 * WaitForOlderSnapshots
 *
 * Wait for transactions that might have an older snapshot than the given xmin
 * limit, because it might not contain tuples deleted just before it has
 * been taken. Obtain a list of VXIDs of such transactions, and wait for them
 * individually. This is used when building an index concurrently.
 *
 * We can exclude any running transactions that have xmin > the xmin given;
 * their oldest snapshot must be newer than our xmin limit.
 * We can also exclude any transactions that have xmin = zero, since they
 * evidently have no live snapshot at all (and any one they might be in
 * process of taking is certainly newer than ours).  Transactions in other
 * DBs can be ignored too, since they'll never even be able to see the
 * index being worked on.
 *
 * We can also exclude autovacuum processes and processes running manual
 * lazy VACUUMs, because they won't be fazed by missing index entries
 * either.  (Manual ANALYZEs, however, can't be excluded because they
 * might be within transactions that are going to do arbitrary operations
 * later.)
 *
 * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
 * check for that.
 *
 * If a process goes idle-in-transaction with xmin zero, we do not need to
 * wait for it anymore, per the above argument.  We do not have the
 * infrastructure right now to stop waiting if that happens, but we can at
 * least avoid the folly of waiting when it is idle at the time we would
 * begin to wait.  We do this by repeatedly rechecking the output of
 * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
 * doesn't show up in the output, we know we can forget about it.
 */
static void
WaitForOlderSnapshots(TransactionId limitXmin, bool progress)
{
    int         n_old_snapshots;
    int         i;
    VirtualTransactionId *old_snapshots;

    old_snapshots = GetCurrentVirtualXIDs(limitXmin, true, false,
                                          PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
                                          &n_old_snapshots);
    if (progress)
        pgstat_progress_update_param(PROGRESS_WAITFOR_TOTAL, n_old_snapshots);

    for (i = 0; i < n_old_snapshots; i++)
    {
        if (!VirtualTransactionIdIsValid(old_snapshots[i]))
            continue;           /* found uninteresting in previous cycle */

        if (i > 0)
        {
            /* see if anything's changed ... */
            VirtualTransactionId *newer_snapshots;
            int         n_newer_snapshots;
            int         j;
            int         k;

            newer_snapshots = GetCurrentVirtualXIDs(limitXmin,
                                                    true, false,
                                                    PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
                                                    &n_newer_snapshots);
            for (j = i; j < n_old_snapshots; j++)
            {
                if (!VirtualTransactionIdIsValid(old_snapshots[j]))
                    continue;   /* found uninteresting in previous cycle */
                for (k = 0; k < n_newer_snapshots; k++)
                {
                    if (VirtualTransactionIdEquals(old_snapshots[j],
                                                   newer_snapshots[k]))
                        break;
                }
                if (k >= n_newer_snapshots) /* not there anymore */
                    SetInvalidVirtualTransactionId(old_snapshots[j]);
            }
            pfree(newer_snapshots);
        }

        if (VirtualTransactionIdIsValid(old_snapshots[i]))
        {
            if (progress)
            {
                PGPROC     *holder = BackendIdGetProc(old_snapshots[i].backendId);

                pgstat_progress_update_param(PROGRESS_WAITFOR_CURRENT_PID,
                                             holder->pid);
            }
            VirtualXactLock(old_snapshots[i], true);
        }

        if (progress)
            pgstat_progress_update_param(PROGRESS_WAITFOR_DONE, i + 1);
    }
}


/*
 * DefineIndex
 *      Creates a new index.
 *
 * 'relationId': the OID of the heap relation on which the index is to be
 *      created
 * 'stmt': IndexStmt describing the properties of the new index.
 * 'indexRelationId': normally InvalidOid, but during bootstrap can be
 *      nonzero to specify a preselected OID for the index.
 * 'parentIndexId': the OID of the parent index; InvalidOid if not the child
 *      of a partitioned index.
 * 'parentConstraintId': the OID of the parent constraint; InvalidOid if not
 *      the child of a constraint (only used when recursing)
 * 'is_alter_table': this is due to an ALTER rather than a CREATE operation.
 * 'check_rights': check for CREATE rights in namespace and tablespace.  (This
 *      should be true except when ALTER is deleting/recreating an index.)
 * 'check_not_in_use': check for table not already in use in current session.
 *      This should be true unless caller is holding the table open, in which
 *      case the caller had better have checked it earlier.
 * 'skip_build': make the catalog entries but don't create the index files
 * 'quiet': suppress the NOTICE chatter ordinarily provided for constraints.
 *
 * Returns the object address of the created index.
 */
ObjectAddress
DefineIndex(Oid relationId,
            IndexStmt *stmt,
            Oid indexRelationId,
            Oid parentIndexId,
            Oid parentConstraintId,
            bool is_alter_table,
            bool check_rights,
            bool check_not_in_use,
            bool skip_build,
            bool quiet)
{
    char       *indexRelationName;
    char       *accessMethodName;
    Oid        *typeObjectId;
    Oid        *collationObjectId;
    Oid        *classObjectId;
    Oid         accessMethodId;
    Oid         namespaceId;
    Oid         tablespaceId;
    Oid         createdConstraintId = InvalidOid;
    List       *indexColNames;
    List       *allIndexParams;
    Relation    rel;
    HeapTuple   tuple;
    Form_pg_am  accessMethodForm;
    IndexAmRoutine *amRoutine;
    bool        amcanorder;
    amoptions_function amoptions;
    bool        partitioned;
    Datum       reloptions;
    int16      *coloptions;
    IndexInfo  *indexInfo;
    bits16      flags;
    bits16      constr_flags;
    int         numberOfAttributes;
    int         numberOfKeyAttributes;
    TransactionId limitXmin;
    ObjectAddress address;
    LockRelId   heaprelid;
    LOCKTAG     heaplocktag;
    LOCKMODE    lockmode;
    Snapshot    snapshot;
    int         save_nestlevel = -1;
    int         i;

    /*
     * Some callers need us to run with an empty default_tablespace; this is a
     * necessary hack to be able to reproduce catalog state accurately when
     * recreating indexes after table-rewriting ALTER TABLE.
     */
    if (stmt->reset_default_tblspc)
    {
        save_nestlevel = NewGUCNestLevel();
        (void) set_config_option("default_tablespace", "",
                                 PGC_USERSET, PGC_S_SESSION,
                                 GUC_ACTION_SAVE, true, 0, false);
    }

    /*
     * Start progress report.  If we're building a partition, this was already
     * done.
     */
    if (!OidIsValid(parentIndexId))
    {
        pgstat_progress_start_command(PROGRESS_COMMAND_CREATE_INDEX,
                                      relationId);
        pgstat_progress_update_param(PROGRESS_CREATEIDX_COMMAND,
                                     stmt->concurrent ?
                                     PROGRESS_CREATEIDX_COMMAND_CREATE_CONCURRENTLY :
                                     PROGRESS_CREATEIDX_COMMAND_CREATE);
    }

    /*
     * No index OID to report yet
     */
    pgstat_progress_update_param(PROGRESS_CREATEIDX_INDEX_OID,
                                 InvalidOid);

    /*
     * count key attributes in index
     */
    numberOfKeyAttributes = list_length(stmt->indexParams);

    /*
     * Calculate the new list of index columns including both key columns and
     * INCLUDE columns.  Later we can determine which of these are key
     * columns, and which are just part of the INCLUDE list by checking the
     * list position.  A list item in a position less than ii_NumIndexKeyAttrs
     * is part of the key columns, and anything equal to and over is part of
     * the INCLUDE columns.
     */
    allIndexParams = list_concat_copy(stmt->indexParams,
                                      stmt->indexIncludingParams);
    numberOfAttributes = list_length(allIndexParams);

    if (numberOfAttributes <= 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                 errmsg("must specify at least one column")));
    if (numberOfAttributes > INDEX_MAX_KEYS)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_COLUMNS),
                 errmsg("cannot use more than %d columns in an index",
                        INDEX_MAX_KEYS)));

    /*
     * Only SELECT ... FOR UPDATE/SHARE are allowed while doing a standard
     * index build; but for concurrent builds we allow INSERT/UPDATE/DELETE
     * (but not VACUUM).
     *
     * NB: Caller is responsible for making sure that relationId refers to the
     * relation on which the index should be built; except in bootstrap mode,
     * this will typically require the caller to have already locked the
     * relation.  To avoid lock upgrade hazards, that lock should be at least
     * as strong as the one we take here.
     *
     * NB: If the lock strength here ever changes, code that is run by
     * parallel workers under the control of certain particular ambuild
     * functions will need to be updated, too.
     */
    lockmode = stmt->concurrent ? ShareUpdateExclusiveLock : ShareLock;
    rel = table_open(relationId, lockmode);

    namespaceId = RelationGetNamespace(rel);

    /* Ensure that it makes sense to index this kind of relation */
    switch (rel->rd_rel->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_MATVIEW:
        case RELKIND_PARTITIONED_TABLE:
            /* OK */
            break;
        case RELKIND_FOREIGN_TABLE:

            /*
             * Custom error message for FOREIGN TABLE since the term is close
             * to a regular table and can confuse the user.
             */
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("cannot create index on foreign table \"%s\"",
                            RelationGetRelationName(rel))));
            break;
        default:
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is not a table or materialized view",
                            RelationGetRelationName(rel))));
            break;
    }

    /*
     * Establish behavior for partitioned tables, and verify sanity of
     * parameters.
     *
     * We do not build an actual index in this case; we only create a few
     * catalog entries.  The actual indexes are built by recursing for each
     * partition.
     */
    partitioned = rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE;
    if (partitioned)
    {
        if (stmt->concurrent)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot create index on partitioned table \"%s\" concurrently",
                            RelationGetRelationName(rel))));
        if (stmt->excludeOpNames)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot create exclusion constraints on partitioned table \"%s\"",
                            RelationGetRelationName(rel))));
    }

    /*
     * Don't try to CREATE INDEX on temp tables of other backends.
     */
    if (RELATION_IS_OTHER_TEMP(rel))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot create indexes on temporary tables of other sessions")));

    /*
     * Unless our caller vouches for having checked this already, insist that
     * the table not be in use by our own session, either.  Otherwise we might
     * fail to make entries in the new index (for instance, if an INSERT or
     * UPDATE is in progress and has already made its list of target indexes).
     */
    if (check_not_in_use)
        CheckTableNotInUse(rel, "CREATE INDEX");

    /*
     * Verify we (still) have CREATE rights in the rel's namespace.
     * (Presumably we did when the rel was created, but maybe not anymore.)
     * Skip check if caller doesn't want it.  Also skip check if
     * bootstrapping, since permissions machinery may not be working yet.
     */
    if (check_rights && !IsBootstrapProcessingMode())
    {
        AclResult   aclresult;

        aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
                                          ACL_CREATE);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, OBJECT_SCHEMA,
                           get_namespace_name(namespaceId));
    }

    /*
     * Select tablespace to use.  If not specified, use default tablespace
     * (which may in turn default to database's default).
     */
    if (stmt->tableSpace)
    {
        tablespaceId = get_tablespace_oid(stmt->tableSpace, false);
        if (partitioned && tablespaceId == MyDatabaseTableSpace)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot specify default tablespace for partitioned relations")));
    }
    else
    {
        tablespaceId = GetDefaultTablespace(rel->rd_rel->relpersistence,
                                            partitioned);
        /* note InvalidOid is OK in this case */
    }

    /* Check tablespace permissions */
    if (check_rights &&
        OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
    {
        AclResult   aclresult;

        aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(),
                                           ACL_CREATE);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, OBJECT_TABLESPACE,
                           get_tablespace_name(tablespaceId));
    }

    /*
     * Force shared indexes into the pg_global tablespace.  This is a bit of a
     * hack but seems simpler than marking them in the BKI commands.  On the
     * other hand, if it's not shared, don't allow it to be placed there.
     */
    if (rel->rd_rel->relisshared)
        tablespaceId = GLOBALTABLESPACE_OID;
    else if (tablespaceId == GLOBALTABLESPACE_OID)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("only shared relations can be placed in pg_global tablespace")));

    /*
     * Choose the index column names.
     */
    indexColNames = ChooseIndexColumnNames(allIndexParams);

    /*
     * Select name for index if caller didn't specify
     */
    indexRelationName = stmt->idxname;
    if (indexRelationName == NULL)
        indexRelationName = ChooseIndexName(RelationGetRelationName(rel),
                                            namespaceId,
                                            indexColNames,
                                            stmt->excludeOpNames,
                                            stmt->primary,
                                            stmt->isconstraint);

    /*
     * look up the access method, verify it can handle the requested features
     */
    accessMethodName = stmt->accessMethod;
    tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
    if (!HeapTupleIsValid(tuple))
    {
        /*
         * Hack to provide more-or-less-transparent updating of old RTREE
         * indexes to GiST: if RTREE is requested and not found, use GIST.
         */
        if (strcmp(accessMethodName, "rtree") == 0)
        {
            ereport(NOTICE,
                    (errmsg("substituting access method \"gist\" for obsolete method \"rtree\"")));
            accessMethodName = "gist";
            tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
        }

        if (!HeapTupleIsValid(tuple))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("access method \"%s\" does not exist",
                            accessMethodName)));
    }
    accessMethodForm = (Form_pg_am) GETSTRUCT(tuple);
    accessMethodId = accessMethodForm->oid;
    amRoutine = GetIndexAmRoutine(accessMethodForm->amhandler);

    pgstat_progress_update_param(PROGRESS_CREATEIDX_ACCESS_METHOD_OID,
                                 accessMethodId);

    if (stmt->unique && !amRoutine->amcanunique)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("access method \"%s\" does not support unique indexes",
                        accessMethodName)));
    if (stmt->indexIncludingParams != NIL && !amRoutine->amcaninclude)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("access method \"%s\" does not support included columns",
                        accessMethodName)));
    if (numberOfAttributes > 1 && !amRoutine->amcanmulticol)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("access method \"%s\" does not support multicolumn indexes",
                        accessMethodName)));
    if (stmt->excludeOpNames && amRoutine->amgettuple == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("access method \"%s\" does not support exclusion constraints",
                        accessMethodName)));

    amcanorder = amRoutine->amcanorder;
    amoptions = amRoutine->amoptions;

    pfree(amRoutine);
    ReleaseSysCache(tuple);

    /*
     * Validate predicate, if given
     */
    if (stmt->whereClause)
        CheckPredicate((Expr *) stmt->whereClause);

    /*
     * Parse AM-specific options, convert to text array form, validate.
     */
    reloptions = transformRelOptions((Datum) 0, stmt->options,
                                     NULL, NULL, false, false);

    (void) index_reloptions(amoptions, reloptions, true);

    /*
     * Prepare arguments for index_create, primarily an IndexInfo structure.
     * Note that predicates must be in implicit-AND format.  In a concurrent
     * build, mark it not-ready-for-inserts.
     */
    indexInfo = makeIndexInfo(numberOfAttributes,
                              numberOfKeyAttributes,
                              accessMethodId,
                              NIL,  /* expressions, NIL for now */
                              make_ands_implicit((Expr *) stmt->whereClause),
                              stmt->unique,
                              !stmt->concurrent,
                              stmt->concurrent);

    typeObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    collationObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    classObjectId = (Oid *) palloc(numberOfAttributes * sizeof(Oid));
    coloptions = (int16 *) palloc(numberOfAttributes * sizeof(int16));
    ComputeIndexAttrs(indexInfo,
                      typeObjectId, collationObjectId, classObjectId,
                      coloptions, allIndexParams,
                      stmt->excludeOpNames, relationId,
                      accessMethodName, accessMethodId,
                      amcanorder, stmt->isconstraint);

    /*
     * Extra checks when creating a PRIMARY KEY index.
     */
    if (stmt->primary)
        index_check_primary_key(rel, indexInfo, is_alter_table, stmt);

    /*
     * If this table is partitioned and we're creating a unique index or a
     * primary key, make sure that the indexed columns are part of the
     * partition key.  Otherwise it would be possible to violate uniqueness by
     * putting values that ought to be unique in different partitions.
     *
     * We could lift this limitation if we had global indexes, but those have
     * their own problems, so this is a useful feature combination.
     */
    if (partitioned && (stmt->unique || stmt->primary))
    {
        PartitionKey key = rel->rd_partkey;
        int         i;

        /*
         * A partitioned table can have unique indexes, as long as all the
         * columns in the partition key appear in the unique key.  A
         * partition-local index can enforce global uniqueness iff the PK
         * value completely determines the partition that a row is in.
         *
         * Thus, verify that all the columns in the partition key appear in
         * the unique key definition.
         */
        for (i = 0; i < key->partnatts; i++)
        {
            bool        found = false;
            int         j;
            const char *constraint_type;

            if (stmt->primary)
                constraint_type = "PRIMARY KEY";
            else if (stmt->unique)
                constraint_type = "UNIQUE";
            else if (stmt->excludeOpNames != NIL)
                constraint_type = "EXCLUDE";
            else
            {
                elog(ERROR, "unknown constraint type");
                constraint_type = NULL; /* keep compiler quiet */
            }

            /*
             * It may be possible to support UNIQUE constraints when partition
             * keys are expressions, but is it worth it?  Give up for now.
             */
            if (key->partattrs[i] == 0)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("unsupported %s constraint with partition key definition",
                                constraint_type),
                         errdetail("%s constraints cannot be used when partition keys include expressions.",
                                   constraint_type)));

            for (j = 0; j < indexInfo->ii_NumIndexKeyAttrs; j++)
            {
                if (key->partattrs[i] == indexInfo->ii_IndexAttrNumbers[j])
                {
                    found = true;
                    break;
                }
            }
            if (!found)
            {
                Form_pg_attribute att;

                att = TupleDescAttr(RelationGetDescr(rel), key->partattrs[i] - 1);
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("insufficient columns in %s constraint definition",
                                constraint_type),
                         errdetail("%s constraint on table \"%s\" lacks column \"%s\" which is part of the partition key.",
                                   constraint_type, RelationGetRelationName(rel),
                                   NameStr(att->attname))));
            }
        }
    }


    /*
     * We disallow indexes on system columns.  They would not necessarily get
     * updated correctly, and they don't seem useful anyway.
     */
    for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
    {
        AttrNumber  attno = indexInfo->ii_IndexAttrNumbers[i];

        if (attno < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("index creation on system columns is not supported")));
    }

    /*
     * Also check for system columns used in expressions or predicates.
     */
    if (indexInfo->ii_Expressions || indexInfo->ii_Predicate)
    {
        Bitmapset  *indexattrs = NULL;

        pull_varattnos((Node *) indexInfo->ii_Expressions, 1, &indexattrs);
        pull_varattnos((Node *) indexInfo->ii_Predicate, 1, &indexattrs);

        for (i = FirstLowInvalidHeapAttributeNumber + 1; i < 0; i++)
        {
            if (bms_is_member(i - FirstLowInvalidHeapAttributeNumber,
                              indexattrs))
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("index creation on system columns is not supported")));
        }
    }

    /*
     * Report index creation if appropriate (delay this till after most of the
     * error checks)
     */
    if (stmt->isconstraint && !quiet)
    {
        const char *constraint_type;

        if (stmt->primary)
            constraint_type = "PRIMARY KEY";
        else if (stmt->unique)
            constraint_type = "UNIQUE";
        else if (stmt->excludeOpNames != NIL)
            constraint_type = "EXCLUDE";
        else
        {
            elog(ERROR, "unknown constraint type");
            constraint_type = NULL; /* keep compiler quiet */
        }

        ereport(DEBUG1,
                (errmsg("%s %s will create implicit index \"%s\" for table \"%s\"",
                        is_alter_table ? "ALTER TABLE / ADD" : "CREATE TABLE /",
                        constraint_type,
                        indexRelationName, RelationGetRelationName(rel))));
    }

    /*
     * A valid stmt->oldNode implies that we already have a built form of the
     * index.  The caller should also decline any index build.
     */
    Assert(!OidIsValid(stmt->oldNode) || (skip_build && !stmt->concurrent));

    /*
     * Make the catalog entries for the index, including constraints. This
     * step also actually builds the index, except if caller requested not to
     * or in concurrent mode, in which case it'll be done later, or doing a
     * partitioned index (because those don't have storage).
     */
    flags = constr_flags = 0;
    if (stmt->isconstraint)
        flags |= INDEX_CREATE_ADD_CONSTRAINT;
    if (skip_build || stmt->concurrent || partitioned)
        flags |= INDEX_CREATE_SKIP_BUILD;
    if (stmt->if_not_exists)
        flags |= INDEX_CREATE_IF_NOT_EXISTS;
    if (stmt->concurrent)
        flags |= INDEX_CREATE_CONCURRENT;
    if (partitioned)
        flags |= INDEX_CREATE_PARTITIONED;
    if (stmt->primary)
        flags |= INDEX_CREATE_IS_PRIMARY;

    /*
     * If the table is partitioned, and recursion was declined but partitions
     * exist, mark the index as invalid.
     */
    if (partitioned && stmt->relation && !stmt->relation->inh)
    {
        PartitionDesc pd = RelationGetPartitionDesc(rel);

        if (pd->nparts != 0)
            flags |= INDEX_CREATE_INVALID;
    }

    if (stmt->deferrable)
        constr_flags |= INDEX_CONSTR_CREATE_DEFERRABLE;
    if (stmt->initdeferred)
        constr_flags |= INDEX_CONSTR_CREATE_INIT_DEFERRED;

    indexRelationId =
        index_create(rel, indexRelationName, indexRelationId, parentIndexId,
                     parentConstraintId,
                     stmt->oldNode, indexInfo, indexColNames,
                     accessMethodId, tablespaceId,
                     collationObjectId, classObjectId,
                     coloptions, reloptions,
                     flags, constr_flags,
                     allowSystemTableMods, !check_rights,
                     &createdConstraintId);

    ObjectAddressSet(address, RelationRelationId, indexRelationId);

    /*
     * Revert to original default_tablespace.  Must do this before any return
     * from this function, but after index_create, so this is a good time.
     */
    if (save_nestlevel >= 0)
        AtEOXact_GUC(true, save_nestlevel);

    if (!OidIsValid(indexRelationId))
    {
        table_close(rel, NoLock);

        /* If this is the top-level index, we're done */
        if (!OidIsValid(parentIndexId))
            pgstat_progress_end_command();

        return address;
    }

    /* Add any requested comment */
    if (stmt->idxcomment != NULL)
        CreateComments(indexRelationId, RelationRelationId, 0,
                       stmt->idxcomment);

    if (partitioned)
    {
        /*
         * Unless caller specified to skip this step (via ONLY), process each
         * partition to make sure they all contain a corresponding index.
         *
         * If we're called internally (no stmt->relation), recurse always.
         */
        if (!stmt->relation || stmt->relation->inh)
        {
            PartitionDesc partdesc = RelationGetPartitionDesc(rel);
            int         nparts = partdesc->nparts;
            Oid        *part_oids = palloc(sizeof(Oid) * nparts);
            bool        invalidate_parent = false;
            TupleDesc   parentDesc;
            Oid        *opfamOids;

            pgstat_progress_update_param(PROGRESS_CREATEIDX_PARTITIONS_TOTAL,
                                         nparts);

            memcpy(part_oids, partdesc->oids, sizeof(Oid) * nparts);

            parentDesc = RelationGetDescr(rel);
            opfamOids = palloc(sizeof(Oid) * numberOfKeyAttributes);
            for (i = 0; i < numberOfKeyAttributes; i++)
                opfamOids[i] = get_opclass_family(classObjectId[i]);

            /*
             * For each partition, scan all existing indexes; if one matches
             * our index definition and is not already attached to some other
             * parent index, attach it to the one we just created.
             *
             * If none matches, build a new index by calling ourselves
             * recursively with the same options (except for the index name).
             */
            for (i = 0; i < nparts; i++)
            {
                Oid         childRelid = part_oids[i];
                Relation    childrel;
                List       *childidxs;
                ListCell   *cell;
                AttrNumber *attmap;
                bool        found = false;
                int         maplen;

                childrel = table_open(childRelid, lockmode);

                /*
                 * Don't try to create indexes on foreign tables, though. Skip
                 * those if a regular index, or fail if trying to create a
                 * constraint index.
                 */
                if (childrel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
                {
                    if (stmt->unique || stmt->primary)
                        ereport(ERROR,
                                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                                 errmsg("cannot create unique index on partitioned table \"%s\"",
                                        RelationGetRelationName(rel)),
                                 errdetail("Table \"%s\" contains partitions that are foreign tables.",
                                           RelationGetRelationName(rel))));

                    table_close(childrel, lockmode);
                    continue;
                }

                childidxs = RelationGetIndexList(childrel);
                attmap =
                    convert_tuples_by_name_map(RelationGetDescr(childrel),
                                               parentDesc,
                                               gettext_noop("could not convert row type"));
                maplen = parentDesc->natts;

                foreach(cell, childidxs)
                {
                    Oid         cldidxid = lfirst_oid(cell);
                    Relation    cldidx;
                    IndexInfo  *cldIdxInfo;

                    /* this index is already partition of another one */
                    if (has_superclass(cldidxid))
                        continue;

                    cldidx = index_open(cldidxid, lockmode);
                    cldIdxInfo = BuildIndexInfo(cldidx);
                    if (CompareIndexInfo(cldIdxInfo, indexInfo,
                                         cldidx->rd_indcollation,
                                         collationObjectId,
                                         cldidx->rd_opfamily,
                                         opfamOids,
                                         attmap, maplen))
                    {
                        Oid         cldConstrOid = InvalidOid;

                        /*
                         * Found a match.
                         *
                         * If this index is being created in the parent
                         * because of a constraint, then the child needs to
                         * have a constraint also, so look for one.  If there
                         * is no such constraint, this index is no good, so
                         * keep looking.
                         */
                        if (createdConstraintId != InvalidOid)
                        {
                            cldConstrOid =
                                get_relation_idx_constraint_oid(childRelid,
                                                                cldidxid);
                            if (cldConstrOid == InvalidOid)
                            {
                                index_close(cldidx, lockmode);
                                continue;
                            }
                        }

                        /* Attach index to parent and we're done. */
                        IndexSetParentIndex(cldidx, indexRelationId);
                        if (createdConstraintId != InvalidOid)
                            ConstraintSetParentConstraint(cldConstrOid,
                                                          createdConstraintId,
                                                          childRelid);

                        if (!cldidx->rd_index->indisvalid)
                            invalidate_parent = true;

                        found = true;
                        /* keep lock till commit */
                        index_close(cldidx, NoLock);
                        break;
                    }

                    index_close(cldidx, lockmode);
                }

                list_free(childidxs);
                table_close(childrel, NoLock);

                /*
                 * If no matching index was found, create our own.
                 */
                if (!found)
                {
                    IndexStmt  *childStmt = copyObject(stmt);
                    bool        found_whole_row;
                    ListCell   *lc;

                    /*
                     * We can't use the same index name for the child index,
                     * so clear idxname to let the recursive invocation choose
                     * a new name.  Likewise, the existing target relation
                     * field is wrong, and if indexOid or oldNode are set,
                     * they mustn't be applied to the child either.
                     */
                    childStmt->idxname = NULL;
                    childStmt->relation = NULL;
                    childStmt->indexOid = InvalidOid;
                    childStmt->oldNode = InvalidOid;

                    /*
                     * Adjust any Vars (both in expressions and in the index's
                     * WHERE clause) to match the partition's column numbering
                     * in case it's different from the parent's.
                     */
                    foreach(lc, childStmt->indexParams)
                    {
                        IndexElem  *ielem = lfirst(lc);

                        /*
                         * If the index parameter is an expression, we must
                         * translate it to contain child Vars.
                         */
                        if (ielem->expr)
                        {
                            ielem->expr =
                                map_variable_attnos((Node *) ielem->expr,
                                                    1, 0, attmap, maplen,
                                                    InvalidOid,
                                                    &found_whole_row);
                            if (found_whole_row)
                                elog(ERROR, "cannot convert whole-row table reference");
                        }
                    }
                    childStmt->whereClause =
                        map_variable_attnos(stmt->whereClause, 1, 0,
                                            attmap, maplen,
                                            InvalidOid, &found_whole_row);
                    if (found_whole_row)
                        elog(ERROR, "cannot convert whole-row table reference");

                    DefineIndex(childRelid, childStmt,
                                InvalidOid, /* no predefined OID */
                                indexRelationId,    /* this is our child */
                                createdConstraintId,
                                is_alter_table, check_rights, check_not_in_use,
                                skip_build, quiet);
                }

                pgstat_progress_update_param(PROGRESS_CREATEIDX_PARTITIONS_DONE,
                                             i + 1);
                pfree(attmap);
            }

            /*
             * The pg_index row we inserted for this index was marked
             * indisvalid=true.  But if we attached an existing index that is
             * invalid, this is incorrect, so update our row to invalid too.
             */
            if (invalidate_parent)
            {
                Relation    pg_index = table_open(IndexRelationId, RowExclusiveLock);
                HeapTuple   tup,
                            newtup;

                tup = SearchSysCache1(INDEXRELID,
                                      ObjectIdGetDatum(indexRelationId));
                if (!HeapTupleIsValid(tup))
                    elog(ERROR, "cache lookup failed for index %u",
                         indexRelationId);
                newtup = heap_copytuple(tup);
                ((Form_pg_index) GETSTRUCT(newtup))->indisvalid = false;
                CatalogTupleUpdate(pg_index, &tup->t_self, newtup);
                ReleaseSysCache(tup);
                table_close(pg_index, RowExclusiveLock);
                heap_freetuple(newtup);
            }
        }

        /*
         * Indexes on partitioned tables are not themselves built, so we're
         * done here.
         */
        table_close(rel, NoLock);
        if (!OidIsValid(parentIndexId))
            pgstat_progress_end_command();
        return address;
    }

    if (!stmt->concurrent)
    {
        /* Close the heap and we're done, in the non-concurrent case */
        table_close(rel, NoLock);

        /* If this is the top-level index, we're done. */
        if (!OidIsValid(parentIndexId))
            pgstat_progress_end_command();

        return address;
    }

    /* save lockrelid and locktag for below, then close rel */
    heaprelid = rel->rd_lockInfo.lockRelId;
    SET_LOCKTAG_RELATION(heaplocktag, heaprelid.dbId, heaprelid.relId);
    table_close(rel, NoLock);

    /*
     * For a concurrent build, it's important to make the catalog entries
     * visible to other transactions before we start to build the index. That
     * will prevent them from making incompatible HOT updates.  The new index
     * will be marked not indisready and not indisvalid, so that no one else
     * tries to either insert into it or use it for queries.
     *
     * We must commit our current transaction so that the index becomes
     * visible; then start another.  Note that all the data structures we just
     * built are lost in the commit.  The only data we keep past here are the
     * relation IDs.
     *
     * Before committing, get a session-level lock on the table, to ensure
     * that neither it nor the index can be dropped before we finish. This
     * cannot block, even if someone else is waiting for access, because we
     * already have the same lock within our transaction.
     *
     * Note: we don't currently bother with a session lock on the index,
     * because there are no operations that could change its state while we
     * hold lock on the parent table.  This might need to change later.
     */
    LockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);

    PopActiveSnapshot();
    CommitTransactionCommand();
    StartTransactionCommand();

    /*
     * The index is now visible, so we can report the OID.
     */
    pgstat_progress_update_param(PROGRESS_CREATEIDX_INDEX_OID,
                                 indexRelationId);

    /*
     * Phase 2 of concurrent index build (see comments for validate_index()
     * for an overview of how this works)
     *
     * Now we must wait until no running transaction could have the table open
     * with the old list of indexes.  Use ShareLock to consider running
     * transactions that hold locks that permit writing to the table.  Note we
     * do not need to worry about xacts that open the table for writing after
     * this point; they will see the new index when they open it.
     *
     * Note: the reason we use actual lock acquisition here, rather than just
     * checking the ProcArray and sleeping, is that deadlock is possible if
     * one of the transactions in question is blocked trying to acquire an
     * exclusive lock on our table.  The lock code will detect deadlock and
     * error out properly.
     */
    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_1);
    WaitForLockers(heaplocktag, ShareLock, true);

    /*
     * At this moment we are sure that there are no transactions with the
     * table open for write that don't have this new index in their list of
     * indexes.  We have waited out all the existing transactions and any new
     * transaction will have the new index in its list, but the index is still
     * marked as "not-ready-for-inserts".  The index is consulted while
     * deciding HOT-safety though.  This arrangement ensures that no new HOT
     * chains can be created where the new tuple and the old tuple in the
     * chain have different index keys.
     *
     * We now take a new snapshot, and build the index using all tuples that
     * are visible in this snapshot.  We can be sure that any HOT updates to
     * these tuples will be compatible with the index, since any updates made
     * by transactions that didn't know about the index are now committed or
     * rolled back.  Thus, each visible tuple is either the end of its
     * HOT-chain or the extension of the chain is HOT-safe for this index.
     */

    /* Set ActiveSnapshot since functions in the indexes may need it */
    PushActiveSnapshot(GetTransactionSnapshot());

    /* Perform concurrent build of index */
    index_concurrently_build(relationId, indexRelationId);

    /* we can do away with our snapshot */
    PopActiveSnapshot();

    /*
     * Commit this transaction to make the indisready update visible.
     */
    CommitTransactionCommand();
    StartTransactionCommand();

    /*
     * Phase 3 of concurrent index build
     *
     * We once again wait until no transaction can have the table open with
     * the index marked as read-only for updates.
     */
    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_2);
    WaitForLockers(heaplocktag, ShareLock, true);

    /*
     * Now take the "reference snapshot" that will be used by validate_index()
     * to filter candidate tuples.  Beware!  There might still be snapshots in
     * use that treat some transaction as in-progress that our reference
     * snapshot treats as committed.  If such a recently-committed transaction
     * deleted tuples in the table, we will not include them in the index; yet
     * those transactions which see the deleting one as still-in-progress will
     * expect such tuples to be there once we mark the index as valid.
     *
     * We solve this by waiting for all endangered transactions to exit before
     * we mark the index as valid.
     *
     * We also set ActiveSnapshot to this snap, since functions in indexes may
     * need a snapshot.
     */
    snapshot = RegisterSnapshot(GetTransactionSnapshot());
    PushActiveSnapshot(snapshot);

    /*
     * Scan the index and the heap, insert any missing index entries.
     */
    validate_index(relationId, indexRelationId, snapshot);

    /*
     * Drop the reference snapshot.  We must do this before waiting out other
     * snapshot holders, else we will deadlock against other processes also
     * doing CREATE INDEX CONCURRENTLY, which would see our snapshot as one
     * they must wait for.  But first, save the snapshot's xmin to use as
     * limitXmin for GetCurrentVirtualXIDs().
     */
    limitXmin = snapshot->xmin;

    PopActiveSnapshot();
    UnregisterSnapshot(snapshot);

    /*
     * The snapshot subsystem could still contain registered snapshots that
     * are holding back our process's advertised xmin; in particular, if
     * default_transaction_isolation = serializable, there is a transaction
     * snapshot that is still active.  The CatalogSnapshot is likewise a
     * hazard.  To ensure no deadlocks, we must commit and start yet another
     * transaction, and do our wait before any snapshot has been taken in it.
     */
    CommitTransactionCommand();
    StartTransactionCommand();

    /* We should now definitely not be advertising any xmin. */
    Assert(MyPgXact->xmin == InvalidTransactionId);

    /*
     * The index is now valid in the sense that it contains all currently
     * interesting tuples.  But since it might not contain tuples deleted just
     * before the reference snap was taken, we have to wait out any
     * transactions that might have older snapshots.
     */
    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_3);
    WaitForOlderSnapshots(limitXmin, true);

    /*
     * Index can now be marked valid -- update its pg_index entry
     */
    index_set_state_flags(indexRelationId, INDEX_CREATE_SET_VALID);

    /*
     * The pg_index update will cause backends (including this one) to update
     * relcache entries for the index itself, but we should also send a
     * relcache inval on the parent table to force replanning of cached plans.
     * Otherwise existing sessions might fail to use the new index where it
     * would be useful.  (Note that our earlier commits did not create reasons
     * to replan; so relcache flush on the index itself was sufficient.)
     */
    CacheInvalidateRelcacheByRelid(heaprelid.relId);

    /*
     * Last thing to do is release the session-level lock on the parent table.
     */
    UnlockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);

    pgstat_progress_end_command();

    return address;
}


/*
 * CheckMutability
 *      Test whether given expression is mutable
 */
static bool
CheckMutability(Expr *expr)
{
    /*
     * First run the expression through the planner.  This has a couple of
     * important consequences.  First, function default arguments will get
     * inserted, which may affect volatility (consider "default now()").
     * Second, inline-able functions will get inlined, which may allow us to
     * conclude that the function is really less volatile than it's marked. As
     * an example, polymorphic functions must be marked with the most volatile
     * behavior that they have for any input type, but once we inline the
     * function we may be able to conclude that it's not so volatile for the
     * particular input type we're dealing with.
     *
     * We assume here that expression_planner() won't scribble on its input.
     */
    expr = expression_planner(expr);

    /* Now we can search for non-immutable functions */
    return contain_mutable_functions((Node *) expr);
}


/*
 * CheckPredicate
 *      Checks that the given partial-index predicate is valid.
 *
 * This used to also constrain the form of the predicate to forms that
 * indxpath.c could do something with.  However, that seems overly
 * restrictive.  One useful application of partial indexes is to apply
 * a UNIQUE constraint across a subset of a table, and in that scenario
 * any evaluable predicate will work.  So accept any predicate here
 * (except ones requiring a plan), and let indxpath.c fend for itself.
 */
static void
CheckPredicate(Expr *predicate)
{
    /*
     * transformExpr() should have already rejected subqueries, aggregates,
     * and window functions, based on the EXPR_KIND_ for a predicate.
     */

    /*
     * A predicate using mutable functions is probably wrong, for the same
     * reasons that we don't allow an index expression to use one.
     */
    if (CheckMutability(predicate))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                 errmsg("functions in index predicate must be marked IMMUTABLE")));
}

/*
 * Compute per-index-column information, including indexed column numbers
 * or index expressions, opclasses, and indoptions. Note, all output vectors
 * should be allocated for all columns, including "including" ones.
 */
static void
ComputeIndexAttrs(IndexInfo *indexInfo,
                  Oid *typeOidP,
                  Oid *collationOidP,
                  Oid *classOidP,
                  int16 *colOptionP,
                  List *attList,    /* list of IndexElem's */
                  List *exclusionOpNames,
                  Oid relId,
                  const char *accessMethodName,
                  Oid accessMethodId,
                  bool amcanorder,
                  bool isconstraint)
{
    ListCell   *nextExclOp;
    ListCell   *lc;
    int         attn;
    int         nkeycols = indexInfo->ii_NumIndexKeyAttrs;

    /* Allocate space for exclusion operator info, if needed */
    if (exclusionOpNames)
    {
        Assert(list_length(exclusionOpNames) == nkeycols);
        indexInfo->ii_ExclusionOps = (Oid *) palloc(sizeof(Oid) * nkeycols);
        indexInfo->ii_ExclusionProcs = (Oid *) palloc(sizeof(Oid) * nkeycols);
        indexInfo->ii_ExclusionStrats = (uint16 *) palloc(sizeof(uint16) * nkeycols);
        nextExclOp = list_head(exclusionOpNames);
    }
    else
        nextExclOp = NULL;

    /*
     * process attributeList
     */
    attn = 0;
    foreach(lc, attList)
    {
        IndexElem  *attribute = (IndexElem *) lfirst(lc);
        Oid         atttype;
        Oid         attcollation;

        /*
         * Process the column-or-expression to be indexed.
         */
        if (attribute->name != NULL)
        {
            /* Simple index attribute */
            HeapTuple   atttuple;
            Form_pg_attribute attform;

            Assert(attribute->expr == NULL);
            atttuple = SearchSysCacheAttName(relId, attribute->name);
            if (!HeapTupleIsValid(atttuple))
            {
                /* difference in error message spellings is historical */
                if (isconstraint)
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_COLUMN),
                             errmsg("column \"%s\" named in key does not exist",
                                    attribute->name)));
                else
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_COLUMN),
                             errmsg("column \"%s\" does not exist",
                                    attribute->name)));
            }
            attform = (Form_pg_attribute) GETSTRUCT(atttuple);
            indexInfo->ii_IndexAttrNumbers[attn] = attform->attnum;
            atttype = attform->atttypid;
            attcollation = attform->attcollation;
            ReleaseSysCache(atttuple);
        }
        else
        {
            /* Index expression */
            Node       *expr = attribute->expr;

            Assert(expr != NULL);

            if (attn >= nkeycols)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("expressions are not supported in included columns")));
            atttype = exprType(expr);
            attcollation = exprCollation(expr);

            /*
             * Strip any top-level COLLATE clause.  This ensures that we treat
             * "x COLLATE y" and "(x COLLATE y)" alike.
             */
            while (IsA(expr, CollateExpr))
                expr = (Node *) ((CollateExpr *) expr)->arg;

            if (IsA(expr, Var) &&
                ((Var *) expr)->varattno != InvalidAttrNumber)
            {
                /*
                 * User wrote "(column)" or "(column COLLATE something)".
                 * Treat it like simple attribute anyway.
                 */
                indexInfo->ii_IndexAttrNumbers[attn] = ((Var *) expr)->varattno;
            }
            else
            {
                indexInfo->ii_IndexAttrNumbers[attn] = 0;   /* marks expression */
                indexInfo->ii_Expressions = lappend(indexInfo->ii_Expressions,
                                                    expr);

                /*
                 * transformExpr() should have already rejected subqueries,
                 * aggregates, and window functions, based on the EXPR_KIND_
                 * for an index expression.
                 */

                /*
                 * An expression using mutable functions is probably wrong,
                 * since if you aren't going to get the same result for the
                 * same data every time, it's not clear what the index entries
                 * mean at all.
                 */
                if (CheckMutability((Expr *) expr))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                             errmsg("functions in index expression must be marked IMMUTABLE")));
            }
        }

        typeOidP[attn] = atttype;

        /*
         * Included columns have no collation, no opclass and no ordering
         * options.
         */
        if (attn >= nkeycols)
        {
            if (attribute->collation)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("including column does not support a collation")));
            if (attribute->opclass)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("including column does not support an operator class")));
            if (attribute->ordering != SORTBY_DEFAULT)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("including column does not support ASC/DESC options")));
            if (attribute->nulls_ordering != SORTBY_NULLS_DEFAULT)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                         errmsg("including column does not support NULLS FIRST/LAST options")));

            classOidP[attn] = InvalidOid;
            colOptionP[attn] = 0;
            collationOidP[attn] = InvalidOid;
            attn++;

            continue;
        }

        /*
         * Apply collation override if any
         */
        if (attribute->collation)
            attcollation = get_collation_oid(attribute->collation, false);

        /*
         * Check we have a collation iff it's a collatable type.  The only
         * expected failures here are (1) COLLATE applied to a noncollatable
         * type, or (2) index expression had an unresolved collation.  But we
         * might as well code this to be a complete consistency check.
         */
        if (type_is_collatable(atttype))
        {
            if (!OidIsValid(attcollation))
                ereport(ERROR,
                        (errcode(ERRCODE_INDETERMINATE_COLLATION),
                         errmsg("could not determine which collation to use for index expression"),
                         errhint("Use the COLLATE clause to set the collation explicitly.")));
        }
        else
        {
            if (OidIsValid(attcollation))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("collations are not supported by type %s",
                                format_type_be(atttype))));
        }

        collationOidP[attn] = attcollation;

        /*
         * Identify the opclass to use.
         */
        classOidP[attn] = ResolveOpClass(attribute->opclass,
                                         atttype,
                                         accessMethodName,
                                         accessMethodId);

        /*
         * Identify the exclusion operator, if any.
         */
        if (nextExclOp)
        {
            List       *opname = (List *) lfirst(nextExclOp);
            Oid         opid;
            Oid         opfamily;
            int         strat;

            /*
             * Find the operator --- it must accept the column datatype
             * without runtime coercion (but binary compatibility is OK)
             */
            opid = compatible_oper_opid(opname, atttype, atttype, false);

            /*
             * Only allow commutative operators to be used in exclusion
             * constraints. If X conflicts with Y, but Y does not conflict
             * with X, bad things will happen.
             */
            if (get_commutator(opid) != opid)
                ereport(ERROR,
                        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                         errmsg("operator %s is not commutative",
                                format_operator(opid)),
                         errdetail("Only commutative operators can be used in exclusion constraints.")));

            /*
             * Operator must be a member of the right opfamily, too
             */
            opfamily = get_opclass_family(classOidP[attn]);
            strat = get_op_opfamily_strategy(opid, opfamily);
            if (strat == 0)
            {
                HeapTuple   opftuple;
                Form_pg_opfamily opfform;

                /*
                 * attribute->opclass might not explicitly name the opfamily,
                 * so fetch the name of the selected opfamily for use in the
                 * error message.
                 */
                opftuple = SearchSysCache1(OPFAMILYOID,
                                           ObjectIdGetDatum(opfamily));
                if (!HeapTupleIsValid(opftuple))
                    elog(ERROR, "cache lookup failed for opfamily %u",
                         opfamily);
                opfform = (Form_pg_opfamily) GETSTRUCT(opftuple);

                ereport(ERROR,
                        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                         errmsg("operator %s is not a member of operator family \"%s\"",
                                format_operator(opid),
                                NameStr(opfform->opfname)),
                         errdetail("The exclusion operator must be related to the index operator class for the constraint.")));
            }

            indexInfo->ii_ExclusionOps[attn] = opid;
            indexInfo->ii_ExclusionProcs[attn] = get_opcode(opid);
            indexInfo->ii_ExclusionStrats[attn] = strat;
            nextExclOp = lnext(exclusionOpNames, nextExclOp);
        }

        /*
         * Set up the per-column options (indoption field).  For now, this is
         * zero for any un-ordered index, while ordered indexes have DESC and
         * NULLS FIRST/LAST options.
         */
        colOptionP[attn] = 0;
        if (amcanorder)
        {
            /* default ordering is ASC */
            if (attribute->ordering == SORTBY_DESC)
                colOptionP[attn] |= INDOPTION_DESC;
            /* default null ordering is LAST for ASC, FIRST for DESC */
            if (attribute->nulls_ordering == SORTBY_NULLS_DEFAULT)
            {
                if (attribute->ordering == SORTBY_DESC)
                    colOptionP[attn] |= INDOPTION_NULLS_FIRST;
            }
            else if (attribute->nulls_ordering == SORTBY_NULLS_FIRST)
                colOptionP[attn] |= INDOPTION_NULLS_FIRST;
        }
        else
        {
            /* index AM does not support ordering */
            if (attribute->ordering != SORTBY_DEFAULT)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("access method \"%s\" does not support ASC/DESC options",
                                accessMethodName)));
            if (attribute->nulls_ordering != SORTBY_NULLS_DEFAULT)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("access method \"%s\" does not support NULLS FIRST/LAST options",
                                accessMethodName)));
        }

        attn++;
    }
}

/*
 * Resolve possibly-defaulted operator class specification
 *
 * Note: This is used to resolve operator class specification in index and
 * partition key definitions.
 */
Oid
ResolveOpClass(List *opclass, Oid attrType,
               const char *accessMethodName, Oid accessMethodId)
{
    char       *schemaname;
    char       *opcname;
    HeapTuple   tuple;
    Form_pg_opclass opform;
    Oid         opClassId,
                opInputType;

    /*
     * Release 7.0 removed network_ops, timespan_ops, and datetime_ops, so we
     * ignore those opclass names so the default *_ops is used.  This can be
     * removed in some later release.  bjm 2000/02/07
     *
     * Release 7.1 removes lztext_ops, so suppress that too for a while.  tgl
     * 2000/07/30
     *
     * Release 7.2 renames timestamp_ops to timestamptz_ops, so suppress that
     * too for awhile.  I'm starting to think we need a better approach. tgl
     * 2000/10/01
     *
     * Release 8.0 removes bigbox_ops (which was dead code for a long while
     * anyway).  tgl 2003/11/11
     */
    if (list_length(opclass) == 1)
    {
        char       *claname = strVal(linitial(opclass));

        if (strcmp(claname, "network_ops") == 0 ||
            strcmp(claname, "timespan_ops") == 0 ||
            strcmp(claname, "datetime_ops") == 0 ||
            strcmp(claname, "lztext_ops") == 0 ||
            strcmp(claname, "timestamp_ops") == 0 ||
            strcmp(claname, "bigbox_ops") == 0)
            opclass = NIL;
    }

    if (opclass == NIL)
    {
        /* no operator class specified, so find the default */
        opClassId = GetDefaultOpClass(attrType, accessMethodId);
        if (!OidIsValid(opClassId))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("data type %s has no default operator class for access method \"%s\"",
                            format_type_be(attrType), accessMethodName),
                     errhint("You must specify an operator class for the index or define a default operator class for the data type.")));
        return opClassId;
    }

    /*
     * Specific opclass name given, so look up the opclass.
     */

    /* deconstruct the name list */
    DeconstructQualifiedName(opclass, &schemaname, &opcname);

    if (schemaname)
    {
        /* Look in specific schema only */
        Oid         namespaceId;

        namespaceId = LookupExplicitNamespace(schemaname, false);
        tuple = SearchSysCache3(CLAAMNAMENSP,
                                ObjectIdGetDatum(accessMethodId),
                                PointerGetDatum(opcname),
                                ObjectIdGetDatum(namespaceId));
    }
    else
    {
        /* Unqualified opclass name, so search the search path */
        opClassId = OpclassnameGetOpcid(accessMethodId, opcname);
        if (!OidIsValid(opClassId))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("operator class \"%s\" does not exist for access method \"%s\"",
                            opcname, accessMethodName)));
        tuple = SearchSysCache1(CLAOID, ObjectIdGetDatum(opClassId));
    }

    if (!HeapTupleIsValid(tuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("operator class \"%s\" does not exist for access method \"%s\"",
                        NameListToString(opclass), accessMethodName)));

    /*
     * Verify that the index operator class accepts this datatype.  Note we
     * will accept binary compatibility.
     */
    opform = (Form_pg_opclass) GETSTRUCT(tuple);
    opClassId = opform->oid;
    opInputType = opform->opcintype;

    if (!IsBinaryCoercible(attrType, opInputType))
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("operator class \"%s\" does not accept data type %s",
                        NameListToString(opclass), format_type_be(attrType))));

    ReleaseSysCache(tuple);

    return opClassId;
}

/*
 * GetDefaultOpClass
 *
 * Given the OIDs of a datatype and an access method, find the default
 * operator class, if any.  Returns InvalidOid if there is none.
 */
Oid
GetDefaultOpClass(Oid type_id, Oid am_id)
{
    Oid         result = InvalidOid;
    int         nexact = 0;
    int         ncompatible = 0;
    int         ncompatiblepreferred = 0;
    Relation    rel;
    ScanKeyData skey[1];
    SysScanDesc scan;
    HeapTuple   tup;
    TYPCATEGORY tcategory;

    /* If it's a domain, look at the base type instead */
    type_id = getBaseType(type_id);

    tcategory = TypeCategory(type_id);

    /*
     * We scan through all the opclasses available for the access method,
     * looking for one that is marked default and matches the target type
     * (either exactly or binary-compatibly, but prefer an exact match).
     *
     * We could find more than one binary-compatible match.  If just one is
     * for a preferred type, use that one; otherwise we fail, forcing the user
     * to specify which one he wants.  (The preferred-type special case is a
     * kluge for varchar: it's binary-compatible to both text and bpchar, so
     * we need a tiebreaker.)  If we find more than one exact match, then
     * someone put bogus entries in pg_opclass.
     */
    rel = table_open(OperatorClassRelationId, AccessShareLock);

    ScanKeyInit(&skey[0],
                Anum_pg_opclass_opcmethod,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(am_id));

    scan = systable_beginscan(rel, OpclassAmNameNspIndexId, true,
                              NULL, 1, skey);

    while (HeapTupleIsValid(tup = systable_getnext(scan)))
    {
        Form_pg_opclass opclass = (Form_pg_opclass) GETSTRUCT(tup);

        /* ignore altogether if not a default opclass */
        if (!opclass->opcdefault)
            continue;
        if (opclass->opcintype == type_id)
        {
            nexact++;
            result = opclass->oid;
        }
        else if (nexact == 0 &&
                 IsBinaryCoercible(type_id, opclass->opcintype))
        {
            if (IsPreferredType(tcategory, opclass->opcintype))
            {
                ncompatiblepreferred++;
                result = opclass->oid;
            }
            else if (ncompatiblepreferred == 0)
            {
                ncompatible++;
                result = opclass->oid;
            }
        }
    }

    systable_endscan(scan);

    table_close(rel, AccessShareLock);

    /* raise error if pg_opclass contains inconsistent data */
    if (nexact > 1)
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("there are multiple default operator classes for data type %s",
                        format_type_be(type_id))));

    if (nexact == 1 ||
        ncompatiblepreferred == 1 ||
        (ncompatiblepreferred == 0 && ncompatible == 1))
        return result;

    return InvalidOid;
}

/*
 *  makeObjectName()
 *
 *  Create a name for an implicitly created index, sequence, constraint,
 *  extended statistics, etc.
 *
 *  The parameters are typically: the original table name, the original field
 *  name, and a "type" string (such as "seq" or "pkey").    The field name
 *  and/or type can be NULL if not relevant.
 *
 *  The result is a palloc'd string.
 *
 *  The basic result we want is "name1_name2_label", omitting "_name2" or
 *  "_label" when those parameters are NULL.  However, we must generate
 *  a name with less than NAMEDATALEN characters!  So, we truncate one or
 *  both names if necessary to make a short-enough string.  The label part
 *  is never truncated (so it had better be reasonably short).
 *
 *  The caller is responsible for checking uniqueness of the generated
 *  name and retrying as needed; retrying will be done by altering the
 *  "label" string (which is why we never truncate that part).
 */
char *
makeObjectName(const char *name1, const char *name2, const char *label)
{
    char       *name;
    int         overhead = 0;   /* chars needed for label and underscores */
    int         availchars;     /* chars available for name(s) */
    int         name1chars;     /* chars allocated to name1 */
    int         name2chars;     /* chars allocated to name2 */
    int         ndx;

    name1chars = strlen(name1);
    if (name2)
    {
        name2chars = strlen(name2);
        overhead++;             /* allow for separating underscore */
    }
    else
        name2chars = 0;
    if (label)
        overhead += strlen(label) + 1;

    availchars = NAMEDATALEN - 1 - overhead;
    Assert(availchars > 0);     /* else caller chose a bad label */

    /*
     * If we must truncate,  preferentially truncate the longer name. This
     * logic could be expressed without a loop, but it's simple and obvious as
     * a loop.
     */
    while (name1chars + name2chars > availchars)
    {
        if (name1chars > name2chars)
            name1chars--;
        else
            name2chars--;
    }

    name1chars = pg_mbcliplen(name1, name1chars, name1chars);
    if (name2)
        name2chars = pg_mbcliplen(name2, name2chars, name2chars);

    /* Now construct the string using the chosen lengths */
    name = palloc(name1chars + name2chars + overhead + 1);
    memcpy(name, name1, name1chars);
    ndx = name1chars;
    if (name2)
    {
        name[ndx++] = '_';
        memcpy(name + ndx, name2, name2chars);
        ndx += name2chars;
    }
    if (label)
    {
        name[ndx++] = '_';
        strcpy(name + ndx, label);
    }
    else
        name[ndx] = '\0';

    return name;
}

/*
 * Select a nonconflicting name for a new relation.  This is ordinarily
 * used to choose index names (which is why it's here) but it can also
 * be used for sequences, or any autogenerated relation kind.
 *
 * name1, name2, and label are used the same way as for makeObjectName(),
 * except that the label can't be NULL; digits will be appended to the label
 * if needed to create a name that is unique within the specified namespace.
 *
 * If isconstraint is true, we also avoid choosing a name matching any
 * existing constraint in the same namespace.  (This is stricter than what
 * Postgres itself requires, but the SQL standard says that constraint names
 * should be unique within schemas, so we follow that for autogenerated
 * constraint names.)
 *
 * Note: it is theoretically possible to get a collision anyway, if someone
 * else chooses the same name concurrently.  This is fairly unlikely to be
 * a problem in practice, especially if one is holding an exclusive lock on
 * the relation identified by name1.  However, if choosing multiple names
 * within a single command, you'd better create the new object and do
 * CommandCounterIncrement before choosing the next one!
 *
 * Returns a palloc'd string.
 */
char *
ChooseRelationName(const char *name1, const char *name2,
                   const char *label, Oid namespaceid,
                   bool isconstraint)
{
    int         pass = 0;
    char       *relname = NULL;
    char        modlabel[NAMEDATALEN];

    /* try the unmodified label first */
    StrNCpy(modlabel, label, sizeof(modlabel));

    for (;;)
    {
        relname = makeObjectName(name1, name2, modlabel);

        if (!OidIsValid(get_relname_relid(relname, namespaceid)))
        {
            if (!isconstraint ||
                !ConstraintNameExists(relname, namespaceid))
                break;
        }

        /* found a conflict, so try a new name component */
        pfree(relname);
        snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass);
    }

    return relname;
}

/*
 * Select the name to be used for an index.
 *
 * The argument list is pretty ad-hoc :-(
 */
static char *
ChooseIndexName(const char *tabname, Oid namespaceId,
                List *colnames, List *exclusionOpNames,
                bool primary, bool isconstraint)
{
    char       *indexname;

    if (primary)
    {
        /* the primary key's name does not depend on the specific column(s) */
        indexname = ChooseRelationName(tabname,
                                       NULL,
                                       "pkey",
                                       namespaceId,
                                       true);
    }
    else if (exclusionOpNames != NIL)
    {
        indexname = ChooseRelationName(tabname,
                                       ChooseIndexNameAddition(colnames),
                                       "excl",
                                       namespaceId,
                                       true);
    }
    else if (isconstraint)
    {
        indexname = ChooseRelationName(tabname,
                                       ChooseIndexNameAddition(colnames),
                                       "key",
                                       namespaceId,
                                       true);
    }
    else
    {
        indexname = ChooseRelationName(tabname,
                                       ChooseIndexNameAddition(colnames),
                                       "idx",
                                       namespaceId,
                                       false);
    }

    return indexname;
}

/*
 * Generate "name2" for a new index given the list of column names for it
 * (as produced by ChooseIndexColumnNames).  This will be passed to
 * ChooseRelationName along with the parent table name and a suitable label.
 *
 * We know that less than NAMEDATALEN characters will actually be used,
 * so we can truncate the result once we've generated that many.
 *
 * XXX See also ChooseForeignKeyConstraintNameAddition and
 * ChooseExtendedStatisticNameAddition.
 */
static char *
ChooseIndexNameAddition(List *colnames)
{
    char        buf[NAMEDATALEN * 2];
    int         buflen = 0;
    ListCell   *lc;

    buf[0] = '\0';
    foreach(lc, colnames)
    {
        const char *name = (const char *) lfirst(lc);

        if (buflen > 0)
            buf[buflen++] = '_';    /* insert _ between names */

        /*
         * At this point we have buflen <= NAMEDATALEN.  name should be less
         * than NAMEDATALEN already, but use strlcpy for paranoia.
         */
        strlcpy(buf + buflen, name, NAMEDATALEN);
        buflen += strlen(buf + buflen);
        if (buflen >= NAMEDATALEN)
            break;
    }
    return pstrdup(buf);
}

/*
 * Select the actual names to be used for the columns of an index, given the
 * list of IndexElems for the columns.  This is mostly about ensuring the
 * names are unique so we don't get a conflicting-attribute-names error.
 *
 * Returns a List of plain strings (char *, not String nodes).
 */
static List *
ChooseIndexColumnNames(List *indexElems)
{
    List       *result = NIL;
    ListCell   *lc;

    foreach(lc, indexElems)
    {
        IndexElem  *ielem = (IndexElem *) lfirst(lc);
        const char *origname;
        const char *curname;
        int         i;
        char        buf[NAMEDATALEN];

        /* Get the preliminary name from the IndexElem */
        if (ielem->indexcolname)
            origname = ielem->indexcolname; /* caller-specified name */
        else if (ielem->name)
            origname = ielem->name; /* simple column reference */
        else
            origname = "expr";  /* default name for expression */

        /* If it conflicts with any previous column, tweak it */
        curname = origname;
        for (i = 1;; i++)
        {
            ListCell   *lc2;
            char        nbuf[32];
            int         nlen;

            foreach(lc2, result)
            {
                if (strcmp(curname, (char *) lfirst(lc2)) == 0)
                    break;
            }
            if (lc2 == NULL)
                break;          /* found nonconflicting name */

            sprintf(nbuf, "%d", i);

            /* Ensure generated names are shorter than NAMEDATALEN */
            nlen = pg_mbcliplen(origname, strlen(origname),
                                NAMEDATALEN - 1 - strlen(nbuf));
            memcpy(buf, origname, nlen);
            strcpy(buf + nlen, nbuf);
            curname = buf;
        }

        /* And attach to the result list */
        result = lappend(result, pstrdup(curname));
    }
    return result;
}

/*
 * ReindexIndex
 *      Recreate a specific index.
 */
void
ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
{
    struct ReindexIndexCallbackState state;
    Oid         indOid;
    Relation    irel;
    char        persistence;

    /*
     * Find and lock index, and check permissions on table; use callback to
     * obtain lock on table first, to avoid deadlock hazard.  The lock level
     * used here must match the index lock obtained in reindex_index().
     */
    state.concurrent = concurrent;
    state.locked_table_oid = InvalidOid;
    indOid = RangeVarGetRelidExtended(indexRelation,
                                      concurrent ? ShareUpdateExclusiveLock : AccessExclusiveLock,
                                      0,
                                      RangeVarCallbackForReindexIndex,
                                      &state);

    /*
     * Obtain the current persistence of the existing index.  We already hold
     * lock on the index.
     */
    irel = index_open(indOid, NoLock);

    if (irel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
    {
        ReindexPartitionedIndex(irel);
        return;
    }

    persistence = irel->rd_rel->relpersistence;
    index_close(irel, NoLock);

    if (concurrent)
        ReindexRelationConcurrently(indOid, options);
    else
        reindex_index(indOid, false, persistence, options);
}

/*
 * Check permissions on table before acquiring relation lock; also lock
 * the heap before the RangeVarGetRelidExtended takes the index lock, to avoid
 * deadlocks.
 */
static void
RangeVarCallbackForReindexIndex(const RangeVar *relation,
                                Oid relId, Oid oldRelId, void *arg)
{
    char        relkind;
    struct ReindexIndexCallbackState *state = arg;
    LOCKMODE    table_lockmode;

    /*
     * Lock level here should match table lock in reindex_index() for
     * non-concurrent case and table locks used by index_concurrently_*() for
     * concurrent case.
     */
    table_lockmode = state->concurrent ? ShareUpdateExclusiveLock : ShareLock;

    /*
     * If we previously locked some other index's heap, and the name we're
     * looking up no longer refers to that relation, release the now-useless
     * lock.
     */
    if (relId != oldRelId && OidIsValid(oldRelId))
    {
        UnlockRelationOid(state->locked_table_oid, table_lockmode);
        state->locked_table_oid = InvalidOid;
    }

    /* If the relation does not exist, there's nothing more to do. */
    if (!OidIsValid(relId))
        return;

    /*
     * If the relation does exist, check whether it's an index.  But note that
     * the relation might have been dropped between the time we did the name
     * lookup and now.  In that case, there's nothing to do.
     */
    relkind = get_rel_relkind(relId);
    if (!relkind)
        return;
    if (relkind != RELKIND_INDEX &&
        relkind != RELKIND_PARTITIONED_INDEX)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not an index", relation->relname)));

    /* Check permissions */
    if (!pg_class_ownercheck(relId, GetUserId()))
        aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_INDEX, relation->relname);

    /* Lock heap before index to avoid deadlock. */
    if (relId != oldRelId)
    {
        Oid         table_oid = IndexGetRelation(relId, true);

        /*
         * If the OID isn't valid, it means the index was concurrently
         * dropped, which is not a problem for us; just return normally.
         */
        if (OidIsValid(table_oid))
        {
            LockRelationOid(table_oid, table_lockmode);
            state->locked_table_oid = table_oid;
        }
    }
}

/*
 * ReindexTable
 *      Recreate all indexes of a table (and of its toast table, if any)
 */
Oid
ReindexTable(RangeVar *relation, int options, bool concurrent)
{
    Oid         heapOid;
    bool        result;

    /* The lock level used here should match reindex_relation(). */
    heapOid = RangeVarGetRelidExtended(relation,
                                       concurrent ? ShareUpdateExclusiveLock : ShareLock,
                                       0,
                                       RangeVarCallbackOwnsTable, NULL);

    if (concurrent)
    {
        result = ReindexRelationConcurrently(heapOid, options);

        if (!result)
            ereport(NOTICE,
                    (errmsg("table \"%s\" has no indexes that can be reindexed concurrently",
                            relation->relname)));
    }
    else
    {
        result = reindex_relation(heapOid,
                                  REINDEX_REL_PROCESS_TOAST |
                                  REINDEX_REL_CHECK_CONSTRAINTS,
                                  options);
        if (!result)
            ereport(NOTICE,
                    (errmsg("table \"%s\" has no indexes to reindex",
                            relation->relname)));
    }

    return heapOid;
}

/*
 * ReindexMultipleTables
 *      Recreate indexes of tables selected by objectName/objectKind.
 *
 * To reduce the probability of deadlocks, each table is reindexed in a
 * separate transaction, so we can release the lock on it right away.
 * That means this must not be called within a user transaction block!
 */
void
ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
                      int options, bool concurrent)
{
    Oid         objectOid;
    Relation    relationRelation;
    TableScanDesc scan;
    ScanKeyData scan_keys[1];
    HeapTuple   tuple;
    MemoryContext private_context;
    MemoryContext old;
    List       *relids = NIL;
    ListCell   *l;
    int         num_keys;
    bool        concurrent_warning = false;

    AssertArg(objectName);
    Assert(objectKind == REINDEX_OBJECT_SCHEMA ||
           objectKind == REINDEX_OBJECT_SYSTEM ||
           objectKind == REINDEX_OBJECT_DATABASE);

    if (objectKind == REINDEX_OBJECT_SYSTEM && concurrent)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot reindex system catalogs concurrently")));

    /*
     * Get OID of object to reindex, being the database currently being used
     * by session for a database or for system catalogs, or the schema defined
     * by caller. At the same time do permission checks that need different
     * processing depending on the object type.
     */
    if (objectKind == REINDEX_OBJECT_SCHEMA)
    {
        objectOid = get_namespace_oid(objectName, false);

        if (!pg_namespace_ownercheck(objectOid, GetUserId()))
            aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_SCHEMA,
                           objectName);
    }
    else
    {
        objectOid = MyDatabaseId;

        if (strcmp(objectName, get_database_name(objectOid)) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("can only reindex the currently open database")));
        if (!pg_database_ownercheck(objectOid, GetUserId()))
            aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_DATABASE,
                           objectName);
    }

    /*
     * Create a memory context that will survive forced transaction commits we
     * do below.  Since it is a child of PortalContext, it will go away
     * eventually even if we suffer an error; there's no need for special
     * abort cleanup logic.
     */
    private_context = AllocSetContextCreate(PortalContext,
                                            "ReindexMultipleTables",
                                            ALLOCSET_SMALL_SIZES);

    /*
     * Define the search keys to find the objects to reindex. For a schema, we
     * select target relations using relnamespace, something not necessary for
     * a database-wide operation.
     */
    if (objectKind == REINDEX_OBJECT_SCHEMA)
    {
        num_keys = 1;
        ScanKeyInit(&scan_keys[0],
                    Anum_pg_class_relnamespace,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(objectOid));
    }
    else
        num_keys = 0;

    /*
     * Scan pg_class to build a list of the relations we need to reindex.
     *
     * We only consider plain relations and materialized views here (toast
     * rels will be processed indirectly by reindex_relation).
     */
    relationRelation = table_open(RelationRelationId, AccessShareLock);
    scan = table_beginscan_catalog(relationRelation, num_keys, scan_keys);
    while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
    {
        Form_pg_class classtuple = (Form_pg_class) GETSTRUCT(tuple);
        Oid         relid = classtuple->oid;

        /*
         * Only regular tables and matviews can have indexes, so ignore any
         * other kind of relation.
         *
         * It is tempting to also consider partitioned tables here, but that
         * has the problem that if the children are in the same schema, they
         * would be processed twice.  Maybe we could have a separate list of
         * partitioned tables, and expand that afterwards into relids,
         * ignoring any duplicates.
         */
        if (classtuple->relkind != RELKIND_RELATION &&
            classtuple->relkind != RELKIND_MATVIEW)
            continue;

        /* Skip temp tables of other backends; we can't reindex them at all */
        if (classtuple->relpersistence == RELPERSISTENCE_TEMP &&
            !isTempNamespace(classtuple->relnamespace))
            continue;

        /* Check user/system classification, and optionally skip */
        if (objectKind == REINDEX_OBJECT_SYSTEM &&
            !IsSystemClass(relid, classtuple))
            continue;

        /*
         * The table can be reindexed if the user is superuser, the table
         * owner, or the database/schema owner (but in the latter case, only
         * if it's not a shared relation).  pg_class_ownercheck includes the
         * superuser case, and depending on objectKind we already know that
         * the user has permission to run REINDEX on this database or schema
         * per the permission checks at the beginning of this routine.
         */
        if (classtuple->relisshared &&
            !pg_class_ownercheck(relid, GetUserId()))
            continue;

        /*
         * Skip system tables, since index_create() would reject indexing them
         * concurrently (and it would likely fail if we tried).
         */
        if (concurrent &&
            IsCatalogRelationOid(relid))
        {
            if (!concurrent_warning)
                ereport(WARNING,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("cannot reindex system catalogs concurrently, skipping all")));
            concurrent_warning = true;
            continue;
        }

        /* Save the list of relation OIDs in private context */
        old = MemoryContextSwitchTo(private_context);

        /*
         * We always want to reindex pg_class first if it's selected to be
         * reindexed.  This ensures that if there is any corruption in
         * pg_class' indexes, they will be fixed before we process any other
         * tables.  This is critical because reindexing itself will try to
         * update pg_class.
         */
        if (relid == RelationRelationId)
            relids = lcons_oid(relid, relids);
        else
            relids = lappend_oid(relids, relid);

        MemoryContextSwitchTo(old);
    }
    table_endscan(scan);
    table_close(relationRelation, AccessShareLock);

    /* Now reindex each rel in a separate transaction */
    PopActiveSnapshot();
    CommitTransactionCommand();
    foreach(l, relids)
    {
        Oid         relid = lfirst_oid(l);

        StartTransactionCommand();
        /* functions in indexes may want a snapshot set */
        PushActiveSnapshot(GetTransactionSnapshot());

        if (concurrent)
        {
            (void) ReindexRelationConcurrently(relid, options);
            /* ReindexRelationConcurrently() does the verbose output */
        }
        else
        {
            bool        result;

            result = reindex_relation(relid,
                                      REINDEX_REL_PROCESS_TOAST |
                                      REINDEX_REL_CHECK_CONSTRAINTS,
                                      options);

            if (result && (options & REINDEXOPT_VERBOSE))
                ereport(INFO,
                        (errmsg("table \"%s.%s\" was reindexed",
                                get_namespace_name(get_rel_namespace(relid)),
                                get_rel_name(relid))));

            PopActiveSnapshot();
        }

        CommitTransactionCommand();
    }
    StartTransactionCommand();

    MemoryContextDelete(private_context);
}


/*
 * ReindexRelationConcurrently - process REINDEX CONCURRENTLY for given
 * relation OID
 *
 * 'relationOid' can either belong to an index, a table or a materialized
 * view.  For tables and materialized views, all its indexes will be rebuilt,
 * excluding invalid indexes and any indexes used in exclusion constraints,
 * but including its associated toast table indexes.  For indexes, the index
 * itself will be rebuilt.  If 'relationOid' belongs to a partitioned table
 * then we issue a warning to mention these are not yet supported.
 *
 * The locks taken on parent tables and involved indexes are kept until the
 * transaction is committed, at which point a session lock is taken on each
 * relation.  Both of these protect against concurrent schema changes.
 *
 * Returns true if any indexes have been rebuilt (including toast table's
 * indexes, when relevant), otherwise returns false.
 */
static bool
ReindexRelationConcurrently(Oid relationOid, int options)
{
    List       *heapRelationIds = NIL;
    List       *indexIds = NIL;
    List       *newIndexIds = NIL;
    List       *relationLocks = NIL;
    List       *lockTags = NIL;
    ListCell   *lc,
               *lc2;
    MemoryContext private_context;
    MemoryContext oldcontext;
    char        relkind;
    char       *relationName = NULL;
    char       *relationNamespace = NULL;
    PGRUsage    ru0;

    /*
     * Create a memory context that will survive forced transaction commits we
     * do below.  Since it is a child of PortalContext, it will go away
     * eventually even if we suffer an error; there's no need for special
     * abort cleanup logic.
     */
    private_context = AllocSetContextCreate(PortalContext,
                                            "ReindexConcurrent",
                                            ALLOCSET_SMALL_SIZES);

    if (options & REINDEXOPT_VERBOSE)
    {
        /* Save data needed by REINDEX VERBOSE in private context */
        oldcontext = MemoryContextSwitchTo(private_context);

        relationName = get_rel_name(relationOid);
        relationNamespace = get_namespace_name(get_rel_namespace(relationOid));

        pg_rusage_init(&ru0);

        MemoryContextSwitchTo(oldcontext);
    }

    relkind = get_rel_relkind(relationOid);

    /*
     * Extract the list of indexes that are going to be rebuilt based on the
     * list of relation Oids given by caller.
     */
    switch (relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_MATVIEW:
        case RELKIND_TOASTVALUE:
            {
                /*
                 * In the case of a relation, find all its indexes including
                 * toast indexes.
                 */
                Relation    heapRelation;

                /* Save the list of relation OIDs in private context */
                oldcontext = MemoryContextSwitchTo(private_context);

                /* Track this relation for session locks */
                heapRelationIds = lappend_oid(heapRelationIds, relationOid);

                MemoryContextSwitchTo(oldcontext);

                if (IsCatalogRelationOid(relationOid))
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("cannot reindex system catalogs concurrently")));

                /* Open relation to get its indexes */
                heapRelation = table_open(relationOid, ShareUpdateExclusiveLock);

                /* Add all the valid indexes of relation to list */
                foreach(lc, RelationGetIndexList(heapRelation))
                {
                    Oid         cellOid = lfirst_oid(lc);
                    Relation    indexRelation = index_open(cellOid,
                                                           ShareUpdateExclusiveLock);

                    if (!indexRelation->rd_index->indisvalid)
                        ereport(WARNING,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("cannot reindex invalid index \"%s.%s\" concurrently, skipping",
                                        get_namespace_name(get_rel_namespace(cellOid)),
                                        get_rel_name(cellOid))));
                    else if (indexRelation->rd_index->indisexclusion)
                        ereport(WARNING,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("cannot reindex exclusion constraint index \"%s.%s\" concurrently, skipping",
                                        get_namespace_name(get_rel_namespace(cellOid)),
                                        get_rel_name(cellOid))));
                    else
                    {
                        /* Save the list of relation OIDs in private context */
                        oldcontext = MemoryContextSwitchTo(private_context);

                        indexIds = lappend_oid(indexIds, cellOid);

                        MemoryContextSwitchTo(oldcontext);
                    }

                    index_close(indexRelation, NoLock);
                }

                /* Also add the toast indexes */
                if (OidIsValid(heapRelation->rd_rel->reltoastrelid))
                {
                    Oid         toastOid = heapRelation->rd_rel->reltoastrelid;
                    Relation    toastRelation = table_open(toastOid,
                                                           ShareUpdateExclusiveLock);

                    /* Save the list of relation OIDs in private context */
                    oldcontext = MemoryContextSwitchTo(private_context);

                    /* Track this relation for session locks */
                    heapRelationIds = lappend_oid(heapRelationIds, toastOid);

                    MemoryContextSwitchTo(oldcontext);

                    foreach(lc2, RelationGetIndexList(toastRelation))
                    {
                        Oid         cellOid = lfirst_oid(lc2);
                        Relation    indexRelation = index_open(cellOid,
                                                               ShareUpdateExclusiveLock);

                        if (!indexRelation->rd_index->indisvalid)
                            ereport(WARNING,
                                    (errcode(ERRCODE_INDEX_CORRUPTED),
                                     errmsg("cannot reindex invalid index \"%s.%s\" concurrently, skipping",
                                            get_namespace_name(get_rel_namespace(cellOid)),
                                            get_rel_name(cellOid))));
                        else
                        {
                            /*
                             * Save the list of relation OIDs in private
                             * context
                             */
                            oldcontext = MemoryContextSwitchTo(private_context);

                            indexIds = lappend_oid(indexIds, cellOid);

                            MemoryContextSwitchTo(oldcontext);
                        }

                        index_close(indexRelation, NoLock);
                    }

                    table_close(toastRelation, NoLock);
                }

                table_close(heapRelation, NoLock);
                break;
            }
        case RELKIND_INDEX:
            {
                Oid         heapId = IndexGetRelation(relationOid, false);

                if (IsCatalogRelationOid(heapId))
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("cannot reindex system catalogs concurrently")));

                /* Save the list of relation OIDs in private context */
                oldcontext = MemoryContextSwitchTo(private_context);

                /* Track the heap relation of this index for session locks */
                heapRelationIds = list_make1_oid(heapId);

                /*
                 * Save the list of relation OIDs in private context.  Note
                 * that invalid indexes are allowed here.
                 */
                indexIds = lappend_oid(indexIds, relationOid);

                MemoryContextSwitchTo(oldcontext);
                break;
            }
        case RELKIND_PARTITIONED_TABLE:
            /* see reindex_relation() */
            ereport(WARNING,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("REINDEX of partitioned tables is not yet implemented, skipping \"%s\"",
                            get_rel_name(relationOid))));
            return false;
        default:
            /* Return error if type of relation is not supported */
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("cannot reindex this type of relation concurrently")));
            break;
    }

    /* Definitely no indexes, so leave */
    if (indexIds == NIL)
    {
        PopActiveSnapshot();
        return false;
    }

    Assert(heapRelationIds != NIL);

    /*-----
     * Now we have all the indexes we want to process in indexIds.
     *
     * The phases now are:
     *
     * 1. create new indexes in the catalog
     * 2. build new indexes
     * 3. let new indexes catch up with tuples inserted in the meantime
     * 4. swap index names
     * 5. mark old indexes as dead
     * 6. drop old indexes
     *
     * We process each phase for all indexes before moving to the next phase,
     * for efficiency.
     */

    /*
     * Phase 1 of REINDEX CONCURRENTLY
     *
     * Create a new index with the same properties as the old one, but it is
     * only registered in catalogs and will be built later.  Then get session
     * locks on all involved tables.  See analogous code in DefineIndex() for
     * more detailed comments.
     */

    foreach(lc, indexIds)
    {
        char       *concurrentName;
        Oid         indexId = lfirst_oid(lc);
        Oid         newIndexId;
        Relation    indexRel;
        Relation    heapRel;
        Relation    newIndexRel;
        LockRelId  *lockrelid;

        indexRel = index_open(indexId, ShareUpdateExclusiveLock);
        heapRel = table_open(indexRel->rd_index->indrelid,
                             ShareUpdateExclusiveLock);

        pgstat_progress_start_command(PROGRESS_COMMAND_CREATE_INDEX,
                                      RelationGetRelid(heapRel));
        pgstat_progress_update_param(PROGRESS_CREATEIDX_COMMAND,
                                     PROGRESS_CREATEIDX_COMMAND_REINDEX_CONCURRENTLY);
        pgstat_progress_update_param(PROGRESS_CREATEIDX_INDEX_OID,
                                     indexId);
        pgstat_progress_update_param(PROGRESS_CREATEIDX_ACCESS_METHOD_OID,
                                     indexRel->rd_rel->relam);

        /* Choose a temporary relation name for the new index */
        concurrentName = ChooseRelationName(get_rel_name(indexId),
                                            NULL,
                                            "ccnew",
                                            get_rel_namespace(indexRel->rd_index->indrelid),
                                            false);

        /* Create new index definition based on given index */
        newIndexId = index_concurrently_create_copy(heapRel,
                                                    indexId,
                                                    concurrentName);

        /* Now open the relation of the new index, a lock is also needed on it */
        newIndexRel = index_open(indexId, ShareUpdateExclusiveLock);

        /*
         * Save the list of OIDs and locks in private context
         */
        oldcontext = MemoryContextSwitchTo(private_context);

        newIndexIds = lappend_oid(newIndexIds, newIndexId);

        /*
         * Save lockrelid to protect each relation from drop then close
         * relations. The lockrelid on parent relation is not taken here to
         * avoid multiple locks taken on the same relation, instead we rely on
         * parentRelationIds built earlier.
         */
        lockrelid = palloc(sizeof(*lockrelid));
        *lockrelid = indexRel->rd_lockInfo.lockRelId;
        relationLocks = lappend(relationLocks, lockrelid);
        lockrelid = palloc(sizeof(*lockrelid));
        *lockrelid = newIndexRel->rd_lockInfo.lockRelId;
        relationLocks = lappend(relationLocks, lockrelid);

        MemoryContextSwitchTo(oldcontext);

        index_close(indexRel, NoLock);
        index_close(newIndexRel, NoLock);
        table_close(heapRel, NoLock);
    }

    /*
     * Save the heap lock for following visibility checks with other backends
     * might conflict with this session.
     */
    foreach(lc, heapRelationIds)
    {
        Relation    heapRelation = table_open(lfirst_oid(lc), ShareUpdateExclusiveLock);
        LockRelId  *lockrelid;
        LOCKTAG    *heaplocktag;

        /* Save the list of locks in private context */
        oldcontext = MemoryContextSwitchTo(private_context);

        /* Add lockrelid of heap relation to the list of locked relations */
        lockrelid = palloc(sizeof(*lockrelid));
        *lockrelid = heapRelation->rd_lockInfo.lockRelId;
        relationLocks = lappend(relationLocks, lockrelid);

        heaplocktag = (LOCKTAG *) palloc(sizeof(LOCKTAG));

        /* Save the LOCKTAG for this parent relation for the wait phase */
        SET_LOCKTAG_RELATION(*heaplocktag, lockrelid->dbId, lockrelid->relId);
        lockTags = lappend(lockTags, heaplocktag);

        MemoryContextSwitchTo(oldcontext);

        /* Close heap relation */
        table_close(heapRelation, NoLock);
    }

    /* Get a session-level lock on each table. */
    foreach(lc, relationLocks)
    {
        LockRelId  *lockrelid = (LockRelId *) lfirst(lc);

        LockRelationIdForSession(lockrelid, ShareUpdateExclusiveLock);
    }

    PopActiveSnapshot();
    CommitTransactionCommand();
    StartTransactionCommand();

    /*
     * Phase 2 of REINDEX CONCURRENTLY
     *
     * Build the new indexes in a separate transaction for each index to avoid
     * having open transactions for an unnecessary long time.  But before
     * doing that, wait until no running transactions could have the table of
     * the index open with the old list of indexes.  See "phase 2" in
     * DefineIndex() for more details.
     */

    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_1);
    WaitForLockersMultiple(lockTags, ShareLock, true);
    CommitTransactionCommand();

    forboth(lc, indexIds, lc2, newIndexIds)
    {
        Relation    indexRel;
        Oid         oldIndexId = lfirst_oid(lc);
        Oid         newIndexId = lfirst_oid(lc2);
        Oid         heapId;

        CHECK_FOR_INTERRUPTS();

        /* Start new transaction for this index's concurrent build */
        StartTransactionCommand();

        /* Set ActiveSnapshot since functions in the indexes may need it */
        PushActiveSnapshot(GetTransactionSnapshot());

        /*
         * Index relation has been closed by previous commit, so reopen it to
         * get its information.
         */
        indexRel = index_open(oldIndexId, ShareUpdateExclusiveLock);
        heapId = indexRel->rd_index->indrelid;
        index_close(indexRel, NoLock);

        /* Perform concurrent build of new index */
        index_concurrently_build(heapId, newIndexId);

        PopActiveSnapshot();
        CommitTransactionCommand();
    }
    StartTransactionCommand();

    /*
     * Phase 3 of REINDEX CONCURRENTLY
     *
     * During this phase the old indexes catch up with any new tuples that
     * were created during the previous phase.  See "phase 3" in DefineIndex()
     * for more details.
     */

    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_2);
    WaitForLockersMultiple(lockTags, ShareLock, true);
    CommitTransactionCommand();

    foreach(lc, newIndexIds)
    {
        Oid         newIndexId = lfirst_oid(lc);
        Oid         heapId;
        TransactionId limitXmin;
        Snapshot    snapshot;

        CHECK_FOR_INTERRUPTS();

        StartTransactionCommand();

        heapId = IndexGetRelation(newIndexId, false);

        /*
         * Take the "reference snapshot" that will be used by validate_index()
         * to filter candidate tuples.
         */
        snapshot = RegisterSnapshot(GetTransactionSnapshot());
        PushActiveSnapshot(snapshot);

        validate_index(heapId, newIndexId, snapshot);

        /*
         * We can now do away with our active snapshot, we still need to save
         * the xmin limit to wait for older snapshots.
         */
        limitXmin = snapshot->xmin;

        PopActiveSnapshot();
        UnregisterSnapshot(snapshot);

        /*
         * To ensure no deadlocks, we must commit and start yet another
         * transaction, and do our wait before any snapshot has been taken in
         * it.
         */
        CommitTransactionCommand();
        StartTransactionCommand();

        /*
         * The index is now valid in the sense that it contains all currently
         * interesting tuples.  But since it might not contain tuples deleted
         * just before the reference snap was taken, we have to wait out any
         * transactions that might have older snapshots.
         */
        pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                     PROGRESS_CREATEIDX_PHASE_WAIT_3);
        WaitForOlderSnapshots(limitXmin, true);

        CommitTransactionCommand();
    }

    /*
     * Phase 4 of REINDEX CONCURRENTLY
     *
     * Now that the new indexes have been validated, swap each new index with
     * its corresponding old index.
     *
     * We mark the new indexes as valid and the old indexes as not valid at
     * the same time to make sure we only get constraint violations from the
     * indexes with the correct names.
     */

    StartTransactionCommand();

    forboth(lc, indexIds, lc2, newIndexIds)
    {
        char       *oldName;
        Oid         oldIndexId = lfirst_oid(lc);
        Oid         newIndexId = lfirst_oid(lc2);
        Oid         heapId;

        CHECK_FOR_INTERRUPTS();

        heapId = IndexGetRelation(oldIndexId, false);

        /* Choose a relation name for old index */
        oldName = ChooseRelationName(get_rel_name(oldIndexId),
                                     NULL,
                                     "ccold",
                                     get_rel_namespace(heapId),
                                     false);

        /*
         * Swap old index with the new one.  This also marks the new one as
         * valid and the old one as not valid.
         */
        index_concurrently_swap(newIndexId, oldIndexId, oldName);

        /*
         * Invalidate the relcache for the table, so that after this commit
         * all sessions will refresh any cached plans that might reference the
         * index.
         */
        CacheInvalidateRelcacheByRelid(heapId);

        /*
         * CCI here so that subsequent iterations see the oldName in the
         * catalog and can choose a nonconflicting name for their oldName.
         * Otherwise, this could lead to conflicts if a table has two indexes
         * whose names are equal for the first NAMEDATALEN-minus-a-few
         * characters.
         */
        CommandCounterIncrement();
    }

    /* Commit this transaction and make index swaps visible */
    CommitTransactionCommand();
    StartTransactionCommand();

    /*
     * Phase 5 of REINDEX CONCURRENTLY
     *
     * Mark the old indexes as dead.  First we must wait until no running
     * transaction could be using the index for a query.  See also
     * index_drop() for more details.
     */

    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_4);
    WaitForLockersMultiple(lockTags, AccessExclusiveLock, true);

    foreach(lc, indexIds)
    {
        Oid         oldIndexId = lfirst_oid(lc);
        Oid         heapId;

        CHECK_FOR_INTERRUPTS();
        heapId = IndexGetRelation(oldIndexId, false);
        index_concurrently_set_dead(heapId, oldIndexId);
    }

    /* Commit this transaction to make the updates visible. */
    CommitTransactionCommand();
    StartTransactionCommand();

    /*
     * Phase 6 of REINDEX CONCURRENTLY
     *
     * Drop the old indexes.
     */

    pgstat_progress_update_param(PROGRESS_CREATEIDX_PHASE,
                                 PROGRESS_CREATEIDX_PHASE_WAIT_4);
    WaitForLockersMultiple(lockTags, AccessExclusiveLock, true);

    PushActiveSnapshot(GetTransactionSnapshot());

    {
        ObjectAddresses *objects = new_object_addresses();

        foreach(lc, indexIds)
        {
            Oid         oldIndexId = lfirst_oid(lc);
            ObjectAddress object;

            object.classId = RelationRelationId;
            object.objectId = oldIndexId;
            object.objectSubId = 0;

            add_exact_object_address(&object, objects);
        }

        /*
         * Use PERFORM_DELETION_CONCURRENT_LOCK so that index_drop() uses the
         * right lock level.
         */
        performMultipleDeletions(objects, DROP_RESTRICT,
                                 PERFORM_DELETION_CONCURRENT_LOCK | PERFORM_DELETION_INTERNAL);
    }

    PopActiveSnapshot();
    CommitTransactionCommand();

    /*
     * Finally, release the session-level lock on the table.
     */
    foreach(lc, relationLocks)
    {
        LockRelId  *lockrelid = (LockRelId *) lfirst(lc);

        UnlockRelationIdForSession(lockrelid, ShareUpdateExclusiveLock);
    }

    /* Start a new transaction to finish process properly */
    StartTransactionCommand();

    /* Log what we did */
    if (options & REINDEXOPT_VERBOSE)
    {
        if (relkind == RELKIND_INDEX)
            ereport(INFO,
                    (errmsg("index \"%s.%s\" was reindexed",
                            relationNamespace, relationName),
                     errdetail("%s.",
                               pg_rusage_show(&ru0))));
        else
        {
            foreach(lc, newIndexIds)
            {
                Oid         indOid = lfirst_oid(lc);

                ereport(INFO,
                        (errmsg("index \"%s.%s\" was reindexed",
                                get_namespace_name(get_rel_namespace(indOid)),
                                get_rel_name(indOid))));
                /* Don't show rusage here, since it's not per index. */
            }

            ereport(INFO,
                    (errmsg("table \"%s.%s\" was reindexed",
                            relationNamespace, relationName),
                     errdetail("%s.",
                               pg_rusage_show(&ru0))));
        }
    }

    MemoryContextDelete(private_context);

    pgstat_progress_end_command();

    return true;
}

/*
 *  ReindexPartitionedIndex
 *      Reindex each child of the given partitioned index.
 *
 * Not yet implemented.
 */
static void
ReindexPartitionedIndex(Relation parentIdx)
{
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("REINDEX is not yet implemented for partitioned indexes")));
}

/*
 * Insert or delete an appropriate pg_inherits tuple to make the given index
 * be a partition of the indicated parent index.
 *
 * This also corrects the pg_depend information for the affected index.
 */
void
IndexSetParentIndex(Relation partitionIdx, Oid parentOid)
{
    Relation    pg_inherits;
    ScanKeyData key[2];
    SysScanDesc scan;
    Oid         partRelid = RelationGetRelid(partitionIdx);
    HeapTuple   tuple;
    bool        fix_dependencies;

    /* Make sure this is an index */
    Assert(partitionIdx->rd_rel->relkind == RELKIND_INDEX ||
           partitionIdx->rd_rel->relkind == RELKIND_PARTITIONED_INDEX);

    /*
     * Scan pg_inherits for rows linking our index to some parent.
     */
    pg_inherits = relation_open(InheritsRelationId, RowExclusiveLock);
    ScanKeyInit(&key[0],
                Anum_pg_inherits_inhrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(partRelid));
    ScanKeyInit(&key[1],
                Anum_pg_inherits_inhseqno,
                BTEqualStrategyNumber, F_INT4EQ,
                Int32GetDatum(1));
    scan = systable_beginscan(pg_inherits, InheritsRelidSeqnoIndexId, true,
                              NULL, 2, key);
    tuple = systable_getnext(scan);

    if (!HeapTupleIsValid(tuple))
    {
        if (parentOid == InvalidOid)
        {
            /*
             * No pg_inherits row, and no parent wanted: nothing to do in this
             * case.
             */
            fix_dependencies = false;
        }
        else
        {
            Datum       values[Natts_pg_inherits];
            bool        isnull[Natts_pg_inherits];

            /*
             * No pg_inherits row exists, and we want a parent for this index,
             * so insert it.
             */
            values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(partRelid);
            values[Anum_pg_inherits_inhparent - 1] =
                ObjectIdGetDatum(parentOid);
            values[Anum_pg_inherits_inhseqno - 1] = Int32GetDatum(1);
            memset(isnull, false, sizeof(isnull));

            tuple = heap_form_tuple(RelationGetDescr(pg_inherits),
                                    values, isnull);
            CatalogTupleInsert(pg_inherits, tuple);

            fix_dependencies = true;
        }
    }
    else
    {
        Form_pg_inherits inhForm = (Form_pg_inherits) GETSTRUCT(tuple);

        if (parentOid == InvalidOid)
        {
            /*
             * There exists a pg_inherits row, which we want to clear; do so.
             */
            CatalogTupleDelete(pg_inherits, &tuple->t_self);
            fix_dependencies = true;
        }
        else
        {
            /*
             * A pg_inherits row exists.  If it's the same we want, then we're
             * good; if it differs, that amounts to a corrupt catalog and
             * should not happen.
             */
            if (inhForm->inhparent != parentOid)
            {
                /* unexpected: we should not get called in this case */
                elog(ERROR, "bogus pg_inherit row: inhrelid %u inhparent %u",
                     inhForm->inhrelid, inhForm->inhparent);
            }

            /* already in the right state */
            fix_dependencies = false;
        }
    }

    /* done with pg_inherits */
    systable_endscan(scan);
    relation_close(pg_inherits, RowExclusiveLock);

    /* set relhassubclass if an index partition has been added to the parent */
    if (OidIsValid(parentOid))
        SetRelationHasSubclass(parentOid, true);

    /* set relispartition correctly on the partition */
    update_relispartition(partRelid, OidIsValid(parentOid));

    if (fix_dependencies)
    {
        /*
         * Insert/delete pg_depend rows.  If setting a parent, add PARTITION
         * dependencies on the parent index and the table; if removing a
         * parent, delete PARTITION dependencies.
         */
        if (OidIsValid(parentOid))
        {
            ObjectAddress partIdx;
            ObjectAddress parentIdx;
            ObjectAddress partitionTbl;

            ObjectAddressSet(partIdx, RelationRelationId, partRelid);
            ObjectAddressSet(parentIdx, RelationRelationId, parentOid);
            ObjectAddressSet(partitionTbl, RelationRelationId,
                             partitionIdx->rd_index->indrelid);
            recordDependencyOn(&partIdx, &parentIdx,
                               DEPENDENCY_PARTITION_PRI);
            recordDependencyOn(&partIdx, &partitionTbl,
                               DEPENDENCY_PARTITION_SEC);
        }
        else
        {
            deleteDependencyRecordsForClass(RelationRelationId, partRelid,
                                            RelationRelationId,
                                            DEPENDENCY_PARTITION_PRI);
            deleteDependencyRecordsForClass(RelationRelationId, partRelid,
                                            RelationRelationId,
                                            DEPENDENCY_PARTITION_SEC);
        }

        /* make our updates visible */
        CommandCounterIncrement();
    }
}

/*
 * Subroutine of IndexSetParentIndex to update the relispartition flag of the
 * given index to the given value.
 */
static void
update_relispartition(Oid relationId, bool newval)
{
    HeapTuple   tup;
    Relation    classRel;

    classRel = table_open(RelationRelationId, RowExclusiveLock);
    tup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relationId));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for relation %u", relationId);
    Assert(((Form_pg_class) GETSTRUCT(tup))->relispartition != newval);
    ((Form_pg_class) GETSTRUCT(tup))->relispartition = newval;
    CatalogTupleUpdate(classRel, &tup->t_self, tup);
    heap_freetuple(tup);
    table_close(classRel, RowExclusiveLock);
}