index.c

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/*-------------------------------------------------------------------------
 *
 * index.c
 *    code to create and destroy POSTGRES index relations
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/index.c
 *
 *
 * INTERFACE ROUTINES
 *      index_create()          - Create a cataloged index relation
 *      index_drop()            - Removes index relation from catalogs
 *      BuildIndexInfo()        - Prepare to insert index tuples
 *      FormIndexDatum()        - Construct datum vector for one index tuple
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <unistd.h>

#include "access/amapi.h"
#include "access/multixact.h"
#include "access/relscan.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/visibilitymap.h"
#include "access/xact.h"
#include "bootstrap/bootstrap.h"
#include "catalog/binary_upgrade.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_am.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_constraint_fn.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "catalog/storage.h"
#include "commands/tablecmds.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "parser/parser.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "storage/procarray.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/pg_rusage.h"
#include "utils/syscache.h"
#include "utils/tuplesort.h"
#include "utils/snapmgr.h"
#include "utils/tqual.h"


/* Potentially set by pg_upgrade_support functions */
Oid         binary_upgrade_next_index_pg_class_oid = InvalidOid;

/* state info for validate_index bulkdelete callback */
typedef struct
{
    Tuplesortstate *tuplesort;  /* for sorting the index TIDs */
    /* statistics (for debug purposes only): */
    double      htups,
                itups,
                tups_inserted;
} v_i_state;

/* non-export function prototypes */
static bool relationHasPrimaryKey(Relation rel);
static TupleDesc ConstructTupleDescriptor(Relation heapRelation,
                         IndexInfo *indexInfo,
                         List *indexColNames,
                         Oid accessMethodObjectId,
                         Oid *collationObjectId,
                         Oid *classObjectId);
static void InitializeAttributeOids(Relation indexRelation,
                        int numatts, Oid indexoid);
static void AppendAttributeTuples(Relation indexRelation, int numatts);
static void UpdateIndexRelation(Oid indexoid, Oid heapoid,
                    IndexInfo *indexInfo,
                    Oid *collationOids,
                    Oid *classOids,
                    int16 *coloptions,
                    bool primary,
                    bool isexclusion,
                    bool immediate,
                    bool isvalid);
static void index_update_stats(Relation rel,
                   bool hasindex, bool isprimary,
                   double reltuples);
static void IndexCheckExclusion(Relation heapRelation,
                    Relation indexRelation,
                    IndexInfo *indexInfo);
static inline int64 itemptr_encode(ItemPointer itemptr);
static inline void itemptr_decode(ItemPointer itemptr, int64 encoded);
static bool validate_index_callback(ItemPointer itemptr, void *opaque);
static void validate_index_heapscan(Relation heapRelation,
                        Relation indexRelation,
                        IndexInfo *indexInfo,
                        Snapshot snapshot,
                        v_i_state *state);
static bool ReindexIsCurrentlyProcessingIndex(Oid indexOid);
static void SetReindexProcessing(Oid heapOid, Oid indexOid);
static void ResetReindexProcessing(void);
static void SetReindexPending(List *indexes);
static void RemoveReindexPending(Oid indexOid);
static void ResetReindexPending(void);


/*
 * relationHasPrimaryKey
 *      See whether an existing relation has a primary key.
 *
 * Caller must have suitable lock on the relation.
 *
 * Note: we intentionally do not check IndexIsValid here; that's because this
 * is used to enforce the rule that there can be only one indisprimary index,
 * and we want that to be true even if said index is invalid.
 */
static bool
relationHasPrimaryKey(Relation rel)
{
    bool        result = false;
    List       *indexoidlist;
    ListCell   *indexoidscan;

    /*
     * Get the list of index OIDs for the table from the relcache, and look up
     * each one in the pg_index syscache until we find one marked primary key
     * (hopefully there isn't more than one such).
     */
    indexoidlist = RelationGetIndexList(rel);

    foreach(indexoidscan, indexoidlist)
    {
        Oid         indexoid = lfirst_oid(indexoidscan);
        HeapTuple   indexTuple;

        indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
        if (!HeapTupleIsValid(indexTuple))  /* should not happen */
            elog(ERROR, "cache lookup failed for index %u", indexoid);
        result = ((Form_pg_index) GETSTRUCT(indexTuple))->indisprimary;
        ReleaseSysCache(indexTuple);
        if (result)
            break;
    }

    list_free(indexoidlist);

    return result;
}

/*
 * index_check_primary_key
 *      Apply special checks needed before creating a PRIMARY KEY index
 *
 * This processing used to be in DefineIndex(), but has been split out
 * so that it can be applied during ALTER TABLE ADD PRIMARY KEY USING INDEX.
 *
 * We check for a pre-existing primary key, and that all columns of the index
 * are simple column references (not expressions), and that all those
 * columns are marked NOT NULL.  If they aren't (which can only happen during
 * ALTER TABLE ADD CONSTRAINT, since the parser forces such columns to be
 * created NOT NULL during CREATE TABLE), do an ALTER SET NOT NULL to mark
 * them so --- or fail if they are not in fact nonnull.
 *
 * Caller had better have at least ShareLock on the table, else the not-null
 * checking isn't trustworthy.
 */
void
index_check_primary_key(Relation heapRel,
                        IndexInfo *indexInfo,
                        bool is_alter_table)
{
    List       *cmds;
    int         i;

    /*
     * If ALTER TABLE, check that there isn't already a PRIMARY KEY. In CREATE
     * TABLE, we have faith that the parser rejected multiple pkey clauses;
     * and CREATE INDEX doesn't have a way to say PRIMARY KEY, so it's no
     * problem either.
     */
    if (is_alter_table &&
        relationHasPrimaryKey(heapRel))
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
                 errmsg("multiple primary keys for table \"%s\" are not allowed",
                        RelationGetRelationName(heapRel))));
    }

    /*
     * Check that all of the attributes in a primary key are marked as not
     * null, otherwise attempt to ALTER TABLE .. SET NOT NULL
     */
    cmds = NIL;
    for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
    {
        AttrNumber  attnum = indexInfo->ii_KeyAttrNumbers[i];
        HeapTuple   atttuple;
        Form_pg_attribute attform;

        if (attnum == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("primary keys cannot be expressions")));

        /* System attributes are never null, so no need to check */
        if (attnum < 0)
            continue;

        atttuple = SearchSysCache2(ATTNUM,
                                   ObjectIdGetDatum(RelationGetRelid(heapRel)),
                                   Int16GetDatum(attnum));
        if (!HeapTupleIsValid(atttuple))
            elog(ERROR, "cache lookup failed for attribute %d of relation %u",
                 attnum, RelationGetRelid(heapRel));
        attform = (Form_pg_attribute) GETSTRUCT(atttuple);

        if (!attform->attnotnull)
        {
            /* Add a subcommand to make this one NOT NULL */
            AlterTableCmd *cmd = makeNode(AlterTableCmd);

            cmd->subtype = AT_SetNotNull;
            cmd->name = pstrdup(NameStr(attform->attname));
            cmds = lappend(cmds, cmd);
        }

        ReleaseSysCache(atttuple);
    }

    /*
     * XXX: Shouldn't the ALTER TABLE .. SET NOT NULL cascade to child tables?
     * Currently, since the PRIMARY KEY itself doesn't cascade, we don't
     * cascade the notnull constraint(s) either; but this is pretty debatable.
     *
     * XXX: possible future improvement: when being called from ALTER TABLE,
     * it would be more efficient to merge this with the outer ALTER TABLE, so
     * as to avoid two scans.  But that seems to complicate DefineIndex's API
     * unduly.
     */
    if (cmds)
        AlterTableInternal(RelationGetRelid(heapRel), cmds, false);
}

/*
 *      ConstructTupleDescriptor
 *
 * Build an index tuple descriptor for a new index
 */
static TupleDesc
ConstructTupleDescriptor(Relation heapRelation,
                         IndexInfo *indexInfo,
                         List *indexColNames,
                         Oid accessMethodObjectId,
                         Oid *collationObjectId,
                         Oid *classObjectId)
{
    int         numatts = indexInfo->ii_NumIndexAttrs;
    ListCell   *colnames_item = list_head(indexColNames);
    ListCell   *indexpr_item = list_head(indexInfo->ii_Expressions);
    IndexAmRoutine *amroutine;
    TupleDesc   heapTupDesc;
    TupleDesc   indexTupDesc;
    int         natts;          /* #atts in heap rel --- for error checks */
    int         i;

    /* We need access to the index AM's API struct */
    amroutine = GetIndexAmRoutineByAmId(accessMethodObjectId, false);

    /* ... and to the table's tuple descriptor */
    heapTupDesc = RelationGetDescr(heapRelation);
    natts = RelationGetForm(heapRelation)->relnatts;

    /*
     * allocate the new tuple descriptor
     */
    indexTupDesc = CreateTemplateTupleDesc(numatts, false);

    /*
     * For simple index columns, we copy the pg_attribute row from the parent
     * relation and modify it as necessary.  For expressions we have to cons
     * up a pg_attribute row the hard way.
     */
    for (i = 0; i < numatts; i++)
    {
        AttrNumber  atnum = indexInfo->ii_KeyAttrNumbers[i];
        Form_pg_attribute to = indexTupDesc->attrs[i];
        HeapTuple   tuple;
        Form_pg_type typeTup;
        Form_pg_opclass opclassTup;
        Oid         keyType;

        if (atnum != 0)
        {
            /* Simple index column */
            Form_pg_attribute from;

            if (atnum < 0)
            {
                /*
                 * here we are indexing on a system attribute (-1...-n)
                 */
                from = SystemAttributeDefinition(atnum,
                                                 heapRelation->rd_rel->relhasoids);
            }
            else
            {
                /*
                 * here we are indexing on a normal attribute (1...n)
                 */
                if (atnum > natts)  /* safety check */
                    elog(ERROR, "invalid column number %d", atnum);
                from = heapTupDesc->attrs[AttrNumberGetAttrOffset(atnum)];
            }

            /*
             * now that we've determined the "from", let's copy the tuple desc
             * data...
             */
            memcpy(to, from, ATTRIBUTE_FIXED_PART_SIZE);

            /*
             * Fix the stuff that should not be the same as the underlying
             * attr
             */
            to->attnum = i + 1;

            to->attstattarget = -1;
            to->attcacheoff = -1;
            to->attnotnull = false;
            to->atthasdef = false;
            to->attidentity = '\0';
            to->attislocal = true;
            to->attinhcount = 0;
            to->attcollation = collationObjectId[i];
        }
        else
        {
            /* Expressional index */
            Node       *indexkey;

            MemSet(to, 0, ATTRIBUTE_FIXED_PART_SIZE);

            if (indexpr_item == NULL)   /* shouldn't happen */
                elog(ERROR, "too few entries in indexprs list");
            indexkey = (Node *) lfirst(indexpr_item);
            indexpr_item = lnext(indexpr_item);

            /*
             * Lookup the expression type in pg_type for the type length etc.
             */
            keyType = exprType(indexkey);
            tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(keyType));
            if (!HeapTupleIsValid(tuple))
                elog(ERROR, "cache lookup failed for type %u", keyType);
            typeTup = (Form_pg_type) GETSTRUCT(tuple);

            /*
             * Assign some of the attributes values. Leave the rest as 0.
             */
            to->attnum = i + 1;
            to->atttypid = keyType;
            to->attlen = typeTup->typlen;
            to->attbyval = typeTup->typbyval;
            to->attstorage = typeTup->typstorage;
            to->attalign = typeTup->typalign;
            to->attstattarget = -1;
            to->attcacheoff = -1;
            to->atttypmod = exprTypmod(indexkey);
            to->attislocal = true;
            to->attcollation = collationObjectId[i];

            ReleaseSysCache(tuple);

            /*
             * Make sure the expression yields a type that's safe to store in
             * an index.  We need this defense because we have index opclasses
             * for pseudo-types such as "record", and the actually stored type
             * had better be safe; eg, a named composite type is okay, an
             * anonymous record type is not.  The test is the same as for
             * whether a table column is of a safe type (which is why we
             * needn't check for the non-expression case).
             */
            CheckAttributeType(NameStr(to->attname),
                               to->atttypid, to->attcollation,
                               NIL, false);
        }

        /*
         * We do not yet have the correct relation OID for the index, so just
         * set it invalid for now.  InitializeAttributeOids() will fix it
         * later.
         */
        to->attrelid = InvalidOid;

        /*
         * Set the attribute name as specified by caller.
         */
        if (colnames_item == NULL)  /* shouldn't happen */
            elog(ERROR, "too few entries in colnames list");
        namestrcpy(&to->attname, (const char *) lfirst(colnames_item));
        colnames_item = lnext(colnames_item);

        /*
         * Check the opclass and index AM to see if either provides a keytype
         * (overriding the attribute type).  Opclass takes precedence.
         */
        tuple = SearchSysCache1(CLAOID, ObjectIdGetDatum(classObjectId[i]));
        if (!HeapTupleIsValid(tuple))
            elog(ERROR, "cache lookup failed for opclass %u",
                 classObjectId[i]);
        opclassTup = (Form_pg_opclass) GETSTRUCT(tuple);
        if (OidIsValid(opclassTup->opckeytype))
            keyType = opclassTup->opckeytype;
        else
            keyType = amroutine->amkeytype;

        /*
         * If keytype is specified as ANYELEMENT, and opcintype is ANYARRAY,
         * then the attribute type must be an array (else it'd not have
         * matched this opclass); use its element type.
         */
        if (keyType == ANYELEMENTOID && opclassTup->opcintype == ANYARRAYOID)
        {
            keyType = get_base_element_type(to->atttypid);
            if (!OidIsValid(keyType))
                elog(ERROR, "could not get element type of array type %u",
                     to->atttypid);
        }

        ReleaseSysCache(tuple);

        /*
         * If a key type different from the heap value is specified, update
         * the type-related fields in the index tupdesc.
         */
        if (OidIsValid(keyType) && keyType != to->atttypid)
        {
            tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(keyType));
            if (!HeapTupleIsValid(tuple))
                elog(ERROR, "cache lookup failed for type %u", keyType);
            typeTup = (Form_pg_type) GETSTRUCT(tuple);

            to->atttypid = keyType;
            to->atttypmod = -1;
            to->attlen = typeTup->typlen;
            to->attbyval = typeTup->typbyval;
            to->attalign = typeTup->typalign;
            to->attstorage = typeTup->typstorage;

            ReleaseSysCache(tuple);
        }
    }

    pfree(amroutine);

    return indexTupDesc;
}

/* ----------------------------------------------------------------
 *      InitializeAttributeOids
 * ----------------------------------------------------------------
 */
static void
InitializeAttributeOids(Relation indexRelation,
                        int numatts,
                        Oid indexoid)
{
    TupleDesc   tupleDescriptor;
    int         i;

    tupleDescriptor = RelationGetDescr(indexRelation);

    for (i = 0; i < numatts; i += 1)
        tupleDescriptor->attrs[i]->attrelid = indexoid;
}

/* ----------------------------------------------------------------
 *      AppendAttributeTuples
 * ----------------------------------------------------------------
 */
static void
AppendAttributeTuples(Relation indexRelation, int numatts)
{
    Relation    pg_attribute;
    CatalogIndexState indstate;
    TupleDesc   indexTupDesc;
    int         i;

    /*
     * open the attribute relation and its indexes
     */
    pg_attribute = heap_open(AttributeRelationId, RowExclusiveLock);

    indstate = CatalogOpenIndexes(pg_attribute);

    /*
     * insert data from new index's tupdesc into pg_attribute
     */
    indexTupDesc = RelationGetDescr(indexRelation);

    for (i = 0; i < numatts; i++)
    {
        /*
         * There used to be very grotty code here to set these fields, but I
         * think it's unnecessary.  They should be set already.
         */
        Assert(indexTupDesc->attrs[i]->attnum == i + 1);
        Assert(indexTupDesc->attrs[i]->attcacheoff == -1);

        InsertPgAttributeTuple(pg_attribute, indexTupDesc->attrs[i], indstate);
    }

    CatalogCloseIndexes(indstate);

    heap_close(pg_attribute, RowExclusiveLock);
}

/* ----------------------------------------------------------------
 *      UpdateIndexRelation
 *
 * Construct and insert a new entry in the pg_index catalog
 * ----------------------------------------------------------------
 */
static void
UpdateIndexRelation(Oid indexoid,
                    Oid heapoid,
                    IndexInfo *indexInfo,
                    Oid *collationOids,
                    Oid *classOids,
                    int16 *coloptions,
                    bool primary,
                    bool isexclusion,
                    bool immediate,
                    bool isvalid)
{
    int2vector *indkey;
    oidvector  *indcollation;
    oidvector  *indclass;
    int2vector *indoption;
    Datum       exprsDatum;
    Datum       predDatum;
    Datum       values[Natts_pg_index];
    bool        nulls[Natts_pg_index];
    Relation    pg_index;
    HeapTuple   tuple;
    int         i;

    /*
     * Copy the index key, opclass, and indoption info into arrays (should we
     * make the caller pass them like this to start with?)
     */
    indkey = buildint2vector(NULL, indexInfo->ii_NumIndexAttrs);
    for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
        indkey->values[i] = indexInfo->ii_KeyAttrNumbers[i];
    indcollation = buildoidvector(collationOids, indexInfo->ii_NumIndexAttrs);
    indclass = buildoidvector(classOids, indexInfo->ii_NumIndexAttrs);
    indoption = buildint2vector(coloptions, indexInfo->ii_NumIndexAttrs);

    /*
     * Convert the index expressions (if any) to a text datum
     */
    if (indexInfo->ii_Expressions != NIL)
    {
        char       *exprsString;

        exprsString = nodeToString(indexInfo->ii_Expressions);
        exprsDatum = CStringGetTextDatum(exprsString);
        pfree(exprsString);
    }
    else
        exprsDatum = (Datum) 0;

    /*
     * Convert the index predicate (if any) to a text datum.  Note we convert
     * implicit-AND format to normal explicit-AND for storage.
     */
    if (indexInfo->ii_Predicate != NIL)
    {
        char       *predString;

        predString = nodeToString(make_ands_explicit(indexInfo->ii_Predicate));
        predDatum = CStringGetTextDatum(predString);
        pfree(predString);
    }
    else
        predDatum = (Datum) 0;

    /*
     * open the system catalog index relation
     */
    pg_index = heap_open(IndexRelationId, RowExclusiveLock);

    /*
     * Build a pg_index tuple
     */
    MemSet(nulls, false, sizeof(nulls));

    values[Anum_pg_index_indexrelid - 1] = ObjectIdGetDatum(indexoid);
    values[Anum_pg_index_indrelid - 1] = ObjectIdGetDatum(heapoid);
    values[Anum_pg_index_indnatts - 1] = Int16GetDatum(indexInfo->ii_NumIndexAttrs);
    values[Anum_pg_index_indisunique - 1] = BoolGetDatum(indexInfo->ii_Unique);
    values[Anum_pg_index_indisprimary - 1] = BoolGetDatum(primary);
    values[Anum_pg_index_indisexclusion - 1] = BoolGetDatum(isexclusion);
    values[Anum_pg_index_indimmediate - 1] = BoolGetDatum(immediate);
    values[Anum_pg_index_indisclustered - 1] = BoolGetDatum(false);
    values[Anum_pg_index_indisvalid - 1] = BoolGetDatum(isvalid);
    values[Anum_pg_index_indcheckxmin - 1] = BoolGetDatum(false);
    /* we set isvalid and isready the same way */
    values[Anum_pg_index_indisready - 1] = BoolGetDatum(isvalid);
    values[Anum_pg_index_indislive - 1] = BoolGetDatum(true);
    values[Anum_pg_index_indisreplident - 1] = BoolGetDatum(false);
    values[Anum_pg_index_indkey - 1] = PointerGetDatum(indkey);
    values[Anum_pg_index_indcollation - 1] = PointerGetDatum(indcollation);
    values[Anum_pg_index_indclass - 1] = PointerGetDatum(indclass);
    values[Anum_pg_index_indoption - 1] = PointerGetDatum(indoption);
    values[Anum_pg_index_indexprs - 1] = exprsDatum;
    if (exprsDatum == (Datum) 0)
        nulls[Anum_pg_index_indexprs - 1] = true;
    values[Anum_pg_index_indpred - 1] = predDatum;
    if (predDatum == (Datum) 0)
        nulls[Anum_pg_index_indpred - 1] = true;

    tuple = heap_form_tuple(RelationGetDescr(pg_index), values, nulls);

    /*
     * insert the tuple into the pg_index catalog
     */
    CatalogTupleInsert(pg_index, tuple);

    /*
     * close the relation and free the tuple
     */
    heap_close(pg_index, RowExclusiveLock);
    heap_freetuple(tuple);
}


/*
 * index_create
 *
 * heapRelation: table to build index on (suitably locked by caller)
 * indexRelationName: what it say
 * indexRelationId: normally, pass InvalidOid to let this routine
 *      generate an OID for the index.  During bootstrap this may be
 *      nonzero to specify a preselected OID.
 * relFileNode: normally, pass InvalidOid to get new storage.  May be
 *      nonzero to attach an existing valid build.
 * indexInfo: same info executor uses to insert into the index
 * indexColNames: column names to use for index (List of char *)
 * accessMethodObjectId: OID of index AM to use
 * tableSpaceId: OID of tablespace to use
 * collationObjectId: array of collation OIDs, one per index column
 * classObjectId: array of index opclass OIDs, one per index column
 * coloptions: array of per-index-column indoption settings
 * reloptions: AM-specific options
 * isprimary: index is a PRIMARY KEY
 * isconstraint: index is owned by PRIMARY KEY, UNIQUE, or EXCLUSION constraint
 * deferrable: constraint is DEFERRABLE
 * initdeferred: constraint is INITIALLY DEFERRED
 * allow_system_table_mods: allow table to be a system catalog
 * skip_build: true to skip the index_build() step for the moment; caller
 *      must do it later (typically via reindex_index())
 * concurrent: if true, do not lock the table against writers.  The index
 *      will be marked "invalid" and the caller must take additional steps
 *      to fix it up.
 * is_internal: if true, post creation hook for new index
 * if_not_exists: if true, do not throw an error if a relation with
 *      the same name already exists.
 *
 * Returns the OID of the created index.
 */
Oid
index_create(Relation heapRelation,
             const char *indexRelationName,
             Oid indexRelationId,
             Oid relFileNode,
             IndexInfo *indexInfo,
             List *indexColNames,
             Oid accessMethodObjectId,
             Oid tableSpaceId,
             Oid *collationObjectId,
             Oid *classObjectId,
             int16 *coloptions,
             Datum reloptions,
             bool isprimary,
             bool isconstraint,
             bool deferrable,
             bool initdeferred,
             bool allow_system_table_mods,
             bool skip_build,
             bool concurrent,
             bool is_internal,
             bool if_not_exists)
{
    Oid         heapRelationId = RelationGetRelid(heapRelation);
    Relation    pg_class;
    Relation    indexRelation;
    TupleDesc   indexTupDesc;
    bool        shared_relation;
    bool        mapped_relation;
    bool        is_exclusion;
    Oid         namespaceId;
    int         i;
    char        relpersistence;

    is_exclusion = (indexInfo->ii_ExclusionOps != NULL);

    pg_class = heap_open(RelationRelationId, RowExclusiveLock);

    /*
     * The index will be in the same namespace as its parent table, and is
     * shared across databases if and only if the parent is.  Likewise, it
     * will use the relfilenode map if and only if the parent does; and it
     * inherits the parent's relpersistence.
     */
    namespaceId = RelationGetNamespace(heapRelation);
    shared_relation = heapRelation->rd_rel->relisshared;
    mapped_relation = RelationIsMapped(heapRelation);
    relpersistence = heapRelation->rd_rel->relpersistence;

    /*
     * check parameters
     */
    if (indexInfo->ii_NumIndexAttrs < 1)
        elog(ERROR, "must index at least one column");

    if (!allow_system_table_mods &&
        IsSystemRelation(heapRelation) &&
        IsNormalProcessingMode())
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("user-defined indexes on system catalog tables are not supported")));

    /*
     * concurrent index build on a system catalog is unsafe because we tend to
     * release locks before committing in catalogs
     */
    if (concurrent &&
        IsSystemRelation(heapRelation))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("concurrent index creation on system catalog tables is not supported")));

    /*
     * This case is currently not supported, but there's no way to ask for it
     * in the grammar anyway, so it can't happen.
     */
    if (concurrent && is_exclusion)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg_internal("concurrent index creation for exclusion constraints is not supported")));

    /*
     * We cannot allow indexing a shared relation after initdb (because
     * there's no way to make the entry in other databases' pg_class).
     */
    if (shared_relation && !IsBootstrapProcessingMode())
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("shared indexes cannot be created after initdb")));

    /*
     * Shared relations must be in pg_global, too (last-ditch check)
     */
    if (shared_relation && tableSpaceId != GLOBALTABLESPACE_OID)
        elog(ERROR, "shared relations must be placed in pg_global tablespace");

    if (get_relname_relid(indexRelationName, namespaceId))
    {
        if (if_not_exists)
        {
            ereport(NOTICE,
                    (errcode(ERRCODE_DUPLICATE_TABLE),
                     errmsg("relation \"%s\" already exists, skipping",
                            indexRelationName)));
            heap_close(pg_class, RowExclusiveLock);
            return InvalidOid;
        }

        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_TABLE),
                 errmsg("relation \"%s\" already exists",
                        indexRelationName)));
    }

    /*
     * construct tuple descriptor for index tuples
     */
    indexTupDesc = ConstructTupleDescriptor(heapRelation,
                                            indexInfo,
                                            indexColNames,
                                            accessMethodObjectId,
                                            collationObjectId,
                                            classObjectId);

    /*
     * Allocate an OID for the index, unless we were told what to use.
     *
     * The OID will be the relfilenode as well, so make sure it doesn't
     * collide with either pg_class OIDs or existing physical files.
     */
    if (!OidIsValid(indexRelationId))
    {
        /* Use binary-upgrade override for pg_class.oid/relfilenode? */
        if (IsBinaryUpgrade)
        {
            if (!OidIsValid(binary_upgrade_next_index_pg_class_oid))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("pg_class index OID value not set when in binary upgrade mode")));

            indexRelationId = binary_upgrade_next_index_pg_class_oid;
            binary_upgrade_next_index_pg_class_oid = InvalidOid;
        }
        else
        {
            indexRelationId =
                GetNewRelFileNode(tableSpaceId, pg_class, relpersistence);
        }
    }

    /*
     * create the index relation's relcache entry and physical disk file. (If
     * we fail further down, it's the smgr's responsibility to remove the disk
     * file again.)
     */
    indexRelation = heap_create(indexRelationName,
                                namespaceId,
                                tableSpaceId,
                                indexRelationId,
                                relFileNode,
                                indexTupDesc,
                                RELKIND_INDEX,
                                relpersistence,
                                shared_relation,
                                mapped_relation,
                                allow_system_table_mods);

    Assert(indexRelationId == RelationGetRelid(indexRelation));

    /*
     * Obtain exclusive lock on it.  Although no other backends can see it
     * until we commit, this prevents deadlock-risk complaints from lock
     * manager in cases such as CLUSTER.
     */
    LockRelation(indexRelation, AccessExclusiveLock);

    /*
     * Fill in fields of the index's pg_class entry that are not set correctly
     * by heap_create.
     *
     * XXX should have a cleaner way to create cataloged indexes
     */
    indexRelation->rd_rel->relowner = heapRelation->rd_rel->relowner;
    indexRelation->rd_rel->relam = accessMethodObjectId;
    indexRelation->rd_rel->relhasoids = false;

    /*
     * store index's pg_class entry
     */
    InsertPgClassTuple(pg_class, indexRelation,
                       RelationGetRelid(indexRelation),
                       (Datum) 0,
                       reloptions);

    /* done with pg_class */
    heap_close(pg_class, RowExclusiveLock);

    /*
     * now update the object id's of all the attribute tuple forms in the
     * index relation's tuple descriptor
     */
    InitializeAttributeOids(indexRelation,
                            indexInfo->ii_NumIndexAttrs,
                            indexRelationId);

    /*
     * append ATTRIBUTE tuples for the index
     */
    AppendAttributeTuples(indexRelation, indexInfo->ii_NumIndexAttrs);

    /* ----------------
     *    update pg_index
     *    (append INDEX tuple)
     *
     *    Note that this stows away a representation of "predicate".
     *    (Or, could define a rule to maintain the predicate) --Nels, Feb '92
     * ----------------
     */
    UpdateIndexRelation(indexRelationId, heapRelationId, indexInfo,
                        collationObjectId, classObjectId, coloptions,
                        isprimary, is_exclusion,
                        !deferrable,
                        !concurrent);

    /*
     * Register constraint and dependencies for the index.
     *
     * If the index is from a CONSTRAINT clause, construct a pg_constraint
     * entry.  The index will be linked to the constraint, which in turn is
     * linked to the table.  If it's not a CONSTRAINT, we need to make a
     * dependency directly on the table.
     *
     * We don't need a dependency on the namespace, because there'll be an
     * indirect dependency via our parent table.
     *
     * During bootstrap we can't register any dependencies, and we don't try
     * to make a constraint either.
     */
    if (!IsBootstrapProcessingMode())
    {
        ObjectAddress myself,
                    referenced;

        myself.classId = RelationRelationId;
        myself.objectId = indexRelationId;
        myself.objectSubId = 0;

        if (isconstraint)
        {
            char        constraintType;

            if (isprimary)
                constraintType = CONSTRAINT_PRIMARY;
            else if (indexInfo->ii_Unique)
                constraintType = CONSTRAINT_UNIQUE;
            else if (is_exclusion)
                constraintType = CONSTRAINT_EXCLUSION;
            else
            {
                elog(ERROR, "constraint must be PRIMARY, UNIQUE or EXCLUDE");
                constraintType = 0; /* keep compiler quiet */
            }

            index_constraint_create(heapRelation,
                                    indexRelationId,
                                    indexInfo,
                                    indexRelationName,
                                    constraintType,
                                    deferrable,
                                    initdeferred,
                                    false,  /* already marked primary */
                                    false,  /* pg_index entry is OK */
                                    false,  /* no old dependencies */
                                    allow_system_table_mods,
                                    is_internal);
        }
        else
        {
            bool        have_simple_col = false;

            /* Create auto dependencies on simply-referenced columns */
            for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
            {
                if (indexInfo->ii_KeyAttrNumbers[i] != 0)
                {
                    referenced.classId = RelationRelationId;
                    referenced.objectId = heapRelationId;
                    referenced.objectSubId = indexInfo->ii_KeyAttrNumbers[i];

                    recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);

                    have_simple_col = true;
                }
            }

            /*
             * If there are no simply-referenced columns, give the index an
             * auto dependency on the whole table.  In most cases, this will
             * be redundant, but it might not be if the index expressions and
             * predicate contain no Vars or only whole-row Vars.
             */
            if (!have_simple_col)
            {
                referenced.classId = RelationRelationId;
                referenced.objectId = heapRelationId;
                referenced.objectSubId = 0;

                recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
            }

            /* Non-constraint indexes can't be deferrable */
            Assert(!deferrable);
            Assert(!initdeferred);
        }

        /* Store dependency on collations */
        /* The default collation is pinned, so don't bother recording it */
        for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
        {
            if (OidIsValid(collationObjectId[i]) &&
                collationObjectId[i] != DEFAULT_COLLATION_OID)
            {
                referenced.classId = CollationRelationId;
                referenced.objectId = collationObjectId[i];
                referenced.objectSubId = 0;

                recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
            }
        }

        /* Store dependency on operator classes */
        for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
        {
            referenced.classId = OperatorClassRelationId;
            referenced.objectId = classObjectId[i];
            referenced.objectSubId = 0;

            recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
        }

        /* Store dependencies on anything mentioned in index expressions */
        if (indexInfo->ii_Expressions)
        {
            recordDependencyOnSingleRelExpr(&myself,
                                            (Node *) indexInfo->ii_Expressions,
                                            heapRelationId,
                                            DEPENDENCY_NORMAL,
                                            DEPENDENCY_AUTO, false);
        }

        /* Store dependencies on anything mentioned in predicate */
        if (indexInfo->ii_Predicate)
        {
            recordDependencyOnSingleRelExpr(&myself,
                                            (Node *) indexInfo->ii_Predicate,
                                            heapRelationId,
                                            DEPENDENCY_NORMAL,
                                            DEPENDENCY_AUTO, false);
        }
    }
    else
    {
        /* Bootstrap mode - assert we weren't asked for constraint support */
        Assert(!isconstraint);
        Assert(!deferrable);
        Assert(!initdeferred);
    }

    /* Post creation hook for new index */
    InvokeObjectPostCreateHookArg(RelationRelationId,
                                  indexRelationId, 0, is_internal);

    /*
     * Advance the command counter so that we can see the newly-entered
     * catalog tuples for the index.
     */
    CommandCounterIncrement();

    /*
     * In bootstrap mode, we have to fill in the index strategy structure with
     * information from the catalogs.  If we aren't bootstrapping, then the
     * relcache entry has already been rebuilt thanks to sinval update during
     * CommandCounterIncrement.
     */
    if (IsBootstrapProcessingMode())
        RelationInitIndexAccessInfo(indexRelation);
    else
        Assert(indexRelation->rd_indexcxt != NULL);

    /*
     * If this is bootstrap (initdb) time, then we don't actually fill in the
     * index yet.  We'll be creating more indexes and classes later, so we
     * delay filling them in until just before we're done with bootstrapping.
     * Similarly, if the caller specified skip_build then filling the index is
     * delayed till later (ALTER TABLE can save work in some cases with this).
     * Otherwise, we call the AM routine that constructs the index.
     */
    if (IsBootstrapProcessingMode())
    {
        index_register(heapRelationId, indexRelationId, indexInfo);
    }
    else if (skip_build)
    {
        /*
         * Caller is responsible for filling the index later on.  However,
         * we'd better make sure that the heap relation is correctly marked as
         * having an index.
         */
        index_update_stats(heapRelation,
                           true,
                           isprimary,
                           -1.0);
        /* Make the above update visible */
        CommandCounterIncrement();
    }
    else
    {
        index_build(heapRelation, indexRelation, indexInfo, isprimary, false);
    }

    /*
     * Close the index; but we keep the lock that we acquired above until end
     * of transaction.  Closing the heap is caller's responsibility.
     */
    index_close(indexRelation, NoLock);

    return indexRelationId;
}

/*
 * index_constraint_create
 *
 * Set up a constraint associated with an index.  Return the new constraint's
 * address.
 *
 * heapRelation: table owning the index (must be suitably locked by caller)
 * indexRelationId: OID of the index
 * indexInfo: same info executor uses to insert into the index
 * constraintName: what it say (generally, should match name of index)
 * constraintType: one of CONSTRAINT_PRIMARY, CONSTRAINT_UNIQUE, or
 *      CONSTRAINT_EXCLUSION
 * deferrable: constraint is DEFERRABLE
 * initdeferred: constraint is INITIALLY DEFERRED
 * mark_as_primary: if true, set flags to mark index as primary key
 * update_pgindex: if true, update pg_index row (else caller's done that)
 * remove_old_dependencies: if true, remove existing dependencies of index
 *      on table's columns
 * allow_system_table_mods: allow table to be a system catalog
 * is_internal: index is constructed due to internal process
 */
ObjectAddress
index_constraint_create(Relation heapRelation,
                        Oid indexRelationId,
                        IndexInfo *indexInfo,
                        const char *constraintName,
                        char constraintType,
                        bool deferrable,
                        bool initdeferred,
                        bool mark_as_primary,
                        bool update_pgindex,
                        bool remove_old_dependencies,
                        bool allow_system_table_mods,
                        bool is_internal)
{
    Oid         namespaceId = RelationGetNamespace(heapRelation);
    ObjectAddress myself,
                referenced;
    Oid         conOid;

    /* constraint creation support doesn't work while bootstrapping */
    Assert(!IsBootstrapProcessingMode());

    /* enforce system-table restriction */
    if (!allow_system_table_mods &&
        IsSystemRelation(heapRelation) &&
        IsNormalProcessingMode())
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("user-defined indexes on system catalog tables are not supported")));

    /* primary/unique constraints shouldn't have any expressions */
    if (indexInfo->ii_Expressions &&
        constraintType != CONSTRAINT_EXCLUSION)
        elog(ERROR, "constraints cannot have index expressions");

    /*
     * If we're manufacturing a constraint for a pre-existing index, we need
     * to get rid of the existing auto dependencies for the index (the ones
     * that index_create() would have made instead of calling this function).
     *
     * Note: this code would not necessarily do the right thing if the index
     * has any expressions or predicate, but we'd never be turning such an
     * index into a UNIQUE or PRIMARY KEY constraint.
     */
    if (remove_old_dependencies)
        deleteDependencyRecordsForClass(RelationRelationId, indexRelationId,
                                        RelationRelationId, DEPENDENCY_AUTO);

    /*
     * Construct a pg_constraint entry.
     */
    conOid = CreateConstraintEntry(constraintName,
                                   namespaceId,
                                   constraintType,
                                   deferrable,
                                   initdeferred,
                                   true,
                                   RelationGetRelid(heapRelation),
                                   indexInfo->ii_KeyAttrNumbers,
                                   indexInfo->ii_NumIndexAttrs,
                                   InvalidOid,  /* no domain */
                                   indexRelationId, /* index OID */
                                   InvalidOid,  /* no foreign key */
                                   NULL,
                                   NULL,
                                   NULL,
                                   NULL,
                                   0,
                                   ' ',
                                   ' ',
                                   ' ',
                                   indexInfo->ii_ExclusionOps,
                                   NULL,    /* no check constraint */
                                   NULL,
                                   NULL,
                                   true,    /* islocal */
                                   0,   /* inhcount */
                                   true,    /* noinherit */
                                   is_internal);

    /*
     * Register the index as internally dependent on the constraint.
     *
     * Note that the constraint has a dependency on the table, so we don't
     * need (or want) any direct dependency from the index to the table.
     */
    myself.classId = RelationRelationId;
    myself.objectId = indexRelationId;
    myself.objectSubId = 0;

    referenced.classId = ConstraintRelationId;
    referenced.objectId = conOid;
    referenced.objectSubId = 0;

    recordDependencyOn(&myself, &referenced, DEPENDENCY_INTERNAL);

    /*
     * If the constraint is deferrable, create the deferred uniqueness
     * checking trigger.  (The trigger will be given an internal dependency on
     * the constraint by CreateTrigger.)
     */
    if (deferrable)
    {
        CreateTrigStmt *trigger;

        trigger = makeNode(CreateTrigStmt);
        trigger->trigname = (constraintType == CONSTRAINT_PRIMARY) ?
            "PK_ConstraintTrigger" :
            "Unique_ConstraintTrigger";
        trigger->relation = NULL;
        trigger->funcname = SystemFuncName("unique_key_recheck");
        trigger->args = NIL;
        trigger->row = true;
        trigger->timing = TRIGGER_TYPE_AFTER;
        trigger->events = TRIGGER_TYPE_INSERT | TRIGGER_TYPE_UPDATE;
        trigger->columns = NIL;
        trigger->whenClause = NULL;
        trigger->isconstraint = true;
        trigger->deferrable = true;
        trigger->initdeferred = initdeferred;
        trigger->constrrel = NULL;

        (void) CreateTrigger(trigger, NULL, RelationGetRelid(heapRelation),
                             InvalidOid, conOid, indexRelationId, true);
    }

    /*
     * If needed, mark the table as having a primary key.  We assume it can't
     * have been so marked already, so no need to clear the flag in the other
     * case.
     *
     * Note: this might better be done by callers.  We do it here to avoid
     * exposing index_update_stats() globally, but that wouldn't be necessary
     * if relhaspkey went away.
     */
    if (mark_as_primary)
        index_update_stats(heapRelation,
                           true,
                           true,
                           -1.0);

    /*
     * If needed, mark the index as primary and/or deferred in pg_index.
     *
     * Note: When making an existing index into a constraint, caller must have
     * a table lock that prevents concurrent table updates; otherwise, there
     * is a risk that concurrent readers of the table will miss seeing this
     * index at all.
     */
    if (update_pgindex && (mark_as_primary || deferrable))
    {
        Relation    pg_index;
        HeapTuple   indexTuple;
        Form_pg_index indexForm;
        bool        dirty = false;

        pg_index = heap_open(IndexRelationId, RowExclusiveLock);

        indexTuple = SearchSysCacheCopy1(INDEXRELID,
                                         ObjectIdGetDatum(indexRelationId));
        if (!HeapTupleIsValid(indexTuple))
            elog(ERROR, "cache lookup failed for index %u", indexRelationId);
        indexForm = (Form_pg_index) GETSTRUCT(indexTuple);

        if (mark_as_primary && !indexForm->indisprimary)
        {
            indexForm->indisprimary = true;
            dirty = true;
        }

        if (deferrable && indexForm->indimmediate)
        {
            indexForm->indimmediate = false;
            dirty = true;
        }

        if (dirty)
        {
            CatalogTupleUpdate(pg_index, &indexTuple->t_self, indexTuple);

            InvokeObjectPostAlterHookArg(IndexRelationId, indexRelationId, 0,
                                         InvalidOid, is_internal);
        }

        heap_freetuple(indexTuple);
        heap_close(pg_index, RowExclusiveLock);
    }

    return referenced;
}

/*
 *      index_drop
 *
 * NOTE: this routine should now only be called through performDeletion(),
 * else associated dependencies won't be cleaned up.
 */
void
index_drop(Oid indexId, bool concurrent)
{
    Oid         heapId;
    Relation    userHeapRelation;
    Relation    userIndexRelation;
    Relation    indexRelation;
    HeapTuple   tuple;
    bool        hasexprs;
    LockRelId   heaprelid,
                indexrelid;
    LOCKTAG     heaplocktag;
    LOCKMODE    lockmode;

    /*
     * To drop an index safely, we must grab exclusive lock on its parent
     * table.  Exclusive lock on the index alone is insufficient because
     * another backend might be about to execute a query on the parent table.
     * If it relies on a previously cached list of index OIDs, then it could
     * attempt to access the just-dropped index.  We must therefore take a
     * table lock strong enough to prevent all queries on the table from
     * proceeding until we commit and send out a shared-cache-inval notice
     * that will make them update their index lists.
     *
     * In the concurrent case we avoid this requirement by disabling index use
     * in multiple steps and waiting out any transactions that might be using
     * the index, so we don't need exclusive lock on the parent table. Instead
     * we take ShareUpdateExclusiveLock, to ensure that two sessions aren't
     * doing CREATE/DROP INDEX CONCURRENTLY on the same index.  (We will get
     * AccessExclusiveLock on the index below, once we're sure nobody else is
     * using it.)
     */
    heapId = IndexGetRelation(indexId, false);
    lockmode = concurrent ? ShareUpdateExclusiveLock : AccessExclusiveLock;
    userHeapRelation = heap_open(heapId, lockmode);
    userIndexRelation = index_open(indexId, lockmode);

    /*
     * We might still have open queries using it in our own session, which the
     * above locking won't prevent, so test explicitly.
     */
    CheckTableNotInUse(userIndexRelation, "DROP INDEX");

    /*
     * Drop Index Concurrently is more or less the reverse process of Create
     * Index Concurrently.
     *
     * First we unset indisvalid so queries starting afterwards don't use the
     * index to answer queries anymore.  We have to keep indisready = true so
     * transactions that are still scanning the index can continue to see
     * valid index contents.  For instance, if they are using READ COMMITTED
     * mode, and another transaction makes changes and commits, they need to
     * see those new tuples in the index.
     *
     * After all transactions that could possibly have used the index for
     * queries end, we can unset indisready and indislive, then wait till
     * nobody could be touching it anymore.  (Note: we need indislive because
     * this state must be distinct from the initial state during CREATE INDEX
     * CONCURRENTLY, which has indislive true while indisready and indisvalid
     * are false.  That's because in that state, transactions must examine the
     * index for HOT-safety decisions, while in this state we don't want them
     * to open it at all.)
     *
     * Since all predicate locks on the index are about to be made invalid, we
     * must promote them to predicate locks on the heap.  In the
     * non-concurrent case we can just do that now.  In the concurrent case
     * it's a bit trickier.  The predicate locks must be moved when there are
     * no index scans in progress on the index and no more can subsequently
     * start, so that no new predicate locks can be made on the index.  Also,
     * they must be moved before heap inserts stop maintaining the index, else
     * the conflict with the predicate lock on the index gap could be missed
     * before the lock on the heap relation is in place to detect a conflict
     * based on the heap tuple insert.
     */
    if (concurrent)
    {
        /*
         * We must commit our transaction in order to make the first pg_index
         * state update visible to other sessions.  If the DROP machinery has
         * already performed any other actions (removal of other objects,
         * pg_depend entries, etc), the commit would make those actions
         * permanent, which would leave us with inconsistent catalog state if
         * we fail partway through the following sequence.  Since DROP INDEX
         * CONCURRENTLY is restricted to dropping just one index that has no
         * dependencies, we should get here before anything's been done ---
         * but let's check that to be sure.  We can verify that the current
         * transaction has not executed any transactional updates by checking
         * that no XID has been assigned.
         */
        if (GetTopTransactionIdIfAny() != InvalidTransactionId)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("DROP INDEX CONCURRENTLY must be first action in transaction")));

        /*
         * Mark index invalid by updating its pg_index entry
         */
        index_set_state_flags(indexId, INDEX_DROP_CLEAR_VALID);

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

        /* save lockrelid and locktag for below, then close but keep locks */
        heaprelid = userHeapRelation->rd_lockInfo.lockRelId;
        SET_LOCKTAG_RELATION(heaplocktag, heaprelid.dbId, heaprelid.relId);
        indexrelid = userIndexRelation->rd_lockInfo.lockRelId;

        heap_close(userHeapRelation, NoLock);
        index_close(userIndexRelation, NoLock);

        /*
         * We must commit our current transaction so that the indisvalid
         * update becomes visible to other transactions; then start another.
         * Note that any previously-built data structures 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.
         */
        LockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);
        LockRelationIdForSession(&indexrelid, ShareUpdateExclusiveLock);

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

        /*
         * Now we must wait until no running transaction could be using the
         * index for a query.  Use AccessExclusiveLock here to check for
         * running transactions that hold locks of any kind on the table. Note
         * we do not need to worry about xacts that open the table for reading
         * after this point; they will see the index as invalid when they open
         * the relation.
         *
         * 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.
         */
        WaitForLockers(heaplocktag, AccessExclusiveLock);

        /*
         * No more predicate locks will be acquired on this index, and we're
         * about to stop doing inserts into the index which could show
         * conflicts with existing predicate locks, so now is the time to move
         * them to the heap relation.
         */
        userHeapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
        userIndexRelation = index_open(indexId, ShareUpdateExclusiveLock);
        TransferPredicateLocksToHeapRelation(userIndexRelation);

        /*
         * Now we are sure that nobody uses the index for queries; they just
         * might have it open for updating it.  So now we can unset indisready
         * and indislive, then wait till nobody could be using it at all
         * anymore.
         */
        index_set_state_flags(indexId, INDEX_DROP_SET_DEAD);

        /*
         * Invalidate the relcache for the table, so that after this commit
         * all sessions will refresh the table's index list.  Forgetting just
         * the index's relcache entry is not enough.
         */
        CacheInvalidateRelcache(userHeapRelation);

        /*
         * Close the relations again, though still holding session lock.
         */
        heap_close(userHeapRelation, NoLock);
        index_close(userIndexRelation, NoLock);

        /*
         * Again, commit the transaction to make the pg_index update visible
         * to other sessions.
         */
        CommitTransactionCommand();
        StartTransactionCommand();

        /*
         * Wait till every transaction that saw the old index state has
         * finished.
         */
        WaitForLockers(heaplocktag, AccessExclusiveLock);

        /*
         * Re-open relations to allow us to complete our actions.
         *
         * At this point, nothing should be accessing the index, but lets
         * leave nothing to chance and grab AccessExclusiveLock on the index
         * before the physical deletion.
         */
        userHeapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
        userIndexRelation = index_open(indexId, AccessExclusiveLock);
    }
    else
    {
        /* Not concurrent, so just transfer predicate locks and we're good */
        TransferPredicateLocksToHeapRelation(userIndexRelation);
    }

    /*
     * Schedule physical removal of the files
     */
    RelationDropStorage(userIndexRelation);

    /*
     * Close and flush the index's relcache entry, to ensure relcache doesn't
     * try to rebuild it while we're deleting catalog entries. We keep the
     * lock though.
     */
    index_close(userIndexRelation, NoLock);

    RelationForgetRelation(indexId);

    /*
     * fix INDEX relation, and check for expressional index
     */
    indexRelation = heap_open(IndexRelationId, RowExclusiveLock);

    tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for index %u", indexId);

    hasexprs = !heap_attisnull(tuple, Anum_pg_index_indexprs);

    CatalogTupleDelete(indexRelation, &tuple->t_self);

    ReleaseSysCache(tuple);
    heap_close(indexRelation, RowExclusiveLock);

    /*
     * if it has any expression columns, we might have stored statistics about
     * them.
     */
    if (hasexprs)
        RemoveStatistics(indexId, 0);

    /*
     * fix ATTRIBUTE relation
     */
    DeleteAttributeTuples(indexId);

    /*
     * fix RELATION relation
     */
    DeleteRelationTuple(indexId);

    /*
     * We are presently too lazy to attempt to compute the new correct value
     * of relhasindex (the next VACUUM will fix it if necessary). So there is
     * no need to update the pg_class tuple for the owning relation. But we
     * must send out a shared-cache-inval notice on the owning relation to
     * ensure other backends update their relcache lists of indexes.  (In the
     * concurrent case, this is redundant but harmless.)
     */
    CacheInvalidateRelcache(userHeapRelation);

    /*
     * Close owning rel, but keep lock
     */
    heap_close(userHeapRelation, NoLock);

    /*
     * Release the session locks before we go.
     */
    if (concurrent)
    {
        UnlockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);
        UnlockRelationIdForSession(&indexrelid, ShareUpdateExclusiveLock);
    }
}

/* ----------------------------------------------------------------
 *                      index_build support
 * ----------------------------------------------------------------
 */

/* ----------------
 *      BuildIndexInfo
 *          Construct an IndexInfo record for an open index
 *
 * IndexInfo stores the information about the index that's needed by
 * FormIndexDatum, which is used for both index_build() and later insertion
 * of individual index tuples.  Normally we build an IndexInfo for an index
 * just once per command, and then use it for (potentially) many tuples.
 * ----------------
 */
IndexInfo *
BuildIndexInfo(Relation index)
{
    IndexInfo  *ii = makeNode(IndexInfo);
    Form_pg_index indexStruct = index->rd_index;
    int         i;
    int         numKeys;

    /* check the number of keys, and copy attr numbers into the IndexInfo */
    numKeys = indexStruct->indnatts;
    if (numKeys < 1 || numKeys > INDEX_MAX_KEYS)
        elog(ERROR, "invalid indnatts %d for index %u",
             numKeys, RelationGetRelid(index));
    ii->ii_NumIndexAttrs = numKeys;
    for (i = 0; i < numKeys; i++)
        ii->ii_KeyAttrNumbers[i] = indexStruct->indkey.values[i];

    /* fetch any expressions needed for expressional indexes */
    ii->ii_Expressions = RelationGetIndexExpressions(index);
    ii->ii_ExpressionsState = NIL;

    /* fetch index predicate if any */
    ii->ii_Predicate = RelationGetIndexPredicate(index);
    ii->ii_PredicateState = NULL;

    /* fetch exclusion constraint info if any */
    if (indexStruct->indisexclusion)
    {
        RelationGetExclusionInfo(index,
                                 &ii->ii_ExclusionOps,
                                 &ii->ii_ExclusionProcs,
                                 &ii->ii_ExclusionStrats);
    }
    else
    {
        ii->ii_ExclusionOps = NULL;
        ii->ii_ExclusionProcs = NULL;
        ii->ii_ExclusionStrats = NULL;
    }

    /* other info */
    ii->ii_Unique = indexStruct->indisunique;
    ii->ii_ReadyForInserts = IndexIsReady(indexStruct);
    /* assume not doing speculative insertion for now */
    ii->ii_UniqueOps = NULL;
    ii->ii_UniqueProcs = NULL;
    ii->ii_UniqueStrats = NULL;

    /* initialize index-build state to default */
    ii->ii_Concurrent = false;
    ii->ii_BrokenHotChain = false;

    /* set up for possible use by index AM */
    ii->ii_AmCache = NULL;
    ii->ii_Context = CurrentMemoryContext;

    return ii;
}

/* ----------------
 *      BuildSpeculativeIndexInfo
 *          Add extra state to IndexInfo record
 *
 * For unique indexes, we usually don't want to add info to the IndexInfo for
 * checking uniqueness, since the B-Tree AM handles that directly.  However,
 * in the case of speculative insertion, additional support is required.
 *
 * Do this processing here rather than in BuildIndexInfo() to not incur the
 * overhead in the common non-speculative cases.
 * ----------------
 */
void
BuildSpeculativeIndexInfo(Relation index, IndexInfo *ii)
{
    int         ncols = index->rd_rel->relnatts;
    int         i;

    /*
     * fetch info for checking unique indexes
     */
    Assert(ii->ii_Unique);

    if (index->rd_rel->relam != BTREE_AM_OID)
        elog(ERROR, "unexpected non-btree speculative unique index");

    ii->ii_UniqueOps = (Oid *) palloc(sizeof(Oid) * ncols);
    ii->ii_UniqueProcs = (Oid *) palloc(sizeof(Oid) * ncols);
    ii->ii_UniqueStrats = (uint16 *) palloc(sizeof(uint16) * ncols);

    /*
     * We have to look up the operator's strategy number.  This provides a
     * cross-check that the operator does match the index.
     */
    /* We need the func OIDs and strategy numbers too */
    for (i = 0; i < ncols; i++)
    {
        ii->ii_UniqueStrats[i] = BTEqualStrategyNumber;
        ii->ii_UniqueOps[i] =
            get_opfamily_member(index->rd_opfamily[i],
                                index->rd_opcintype[i],
                                index->rd_opcintype[i],
                                ii->ii_UniqueStrats[i]);
        ii->ii_UniqueProcs[i] = get_opcode(ii->ii_UniqueOps[i]);
    }
}

/* ----------------
 *      FormIndexDatum
 *          Construct values[] and isnull[] arrays for a new index tuple.
 *
 *  indexInfo       Info about the index
 *  slot            Heap tuple for which we must prepare an index entry
 *  estate          executor state for evaluating any index expressions
 *  values          Array of index Datums (output area)
 *  isnull          Array of is-null indicators (output area)
 *
 * When there are no index expressions, estate may be NULL.  Otherwise it
 * must be supplied, *and* the ecxt_scantuple slot of its per-tuple expr
 * context must point to the heap tuple passed in.
 *
 * Notice we don't actually call index_form_tuple() here; we just prepare
 * its input arrays values[] and isnull[].  This is because the index AM
 * may wish to alter the data before storage.
 * ----------------
 */
void
FormIndexDatum(IndexInfo *indexInfo,
               TupleTableSlot *slot,
               EState *estate,
               Datum *values,
               bool *isnull)
{
    ListCell   *indexpr_item;
    int         i;

    if (indexInfo->ii_Expressions != NIL &&
        indexInfo->ii_ExpressionsState == NIL)
    {
        /* First time through, set up expression evaluation state */
        indexInfo->ii_ExpressionsState =
            ExecPrepareExprList(indexInfo->ii_Expressions, estate);
        /* Check caller has set up context correctly */
        Assert(GetPerTupleExprContext(estate)->ecxt_scantuple == slot);
    }
    indexpr_item = list_head(indexInfo->ii_ExpressionsState);

    for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
    {
        int         keycol = indexInfo->ii_KeyAttrNumbers[i];
        Datum       iDatum;
        bool        isNull;

        if (keycol != 0)
        {
            /*
             * Plain index column; get the value we need directly from the
             * heap tuple.
             */
            iDatum = slot_getattr(slot, keycol, &isNull);
        }
        else
        {
            /*
             * Index expression --- need to evaluate it.
             */
            if (indexpr_item == NULL)
                elog(ERROR, "wrong number of index expressions");
            iDatum = ExecEvalExprSwitchContext((ExprState *) lfirst(indexpr_item),
                                               GetPerTupleExprContext(estate),
                                               &isNull);
            indexpr_item = lnext(indexpr_item);
        }
        values[i] = iDatum;
        isnull[i] = isNull;
    }

    if (indexpr_item != NULL)
        elog(ERROR, "wrong number of index expressions");
}


/*
 * index_update_stats --- update pg_class entry after CREATE INDEX or REINDEX
 *
 * This routine updates the pg_class row of either an index or its parent
 * relation after CREATE INDEX or REINDEX.  Its rather bizarre API is designed
 * to ensure we can do all the necessary work in just one update.
 *
 * hasindex: set relhasindex to this value
 * isprimary: if true, set relhaspkey true; else no change
 * reltuples: if >= 0, set reltuples to this value; else no change
 *
 * If reltuples >= 0, relpages and relallvisible are also updated (using
 * RelationGetNumberOfBlocks() and visibilitymap_count()).
 *
 * NOTE: an important side-effect of this operation is that an SI invalidation
 * message is sent out to all backends --- including me --- causing relcache
 * entries to be flushed or updated with the new data.  This must happen even
 * if we find that no change is needed in the pg_class row.  When updating
 * a heap entry, this ensures that other backends find out about the new
 * index.  When updating an index, it's important because some index AMs
 * expect a relcache flush to occur after REINDEX.
 */
static void
index_update_stats(Relation rel,
                   bool hasindex,
                   bool isprimary,
                   double reltuples)
{
    Oid         relid = RelationGetRelid(rel);
    Relation    pg_class;
    HeapTuple   tuple;
    Form_pg_class rd_rel;
    bool        dirty;

    /*
     * We always update the pg_class row using a non-transactional,
     * overwrite-in-place update.  There are several reasons for this:
     *
     * 1. In bootstrap mode, we have no choice --- UPDATE wouldn't work.
     *
     * 2. We could be reindexing pg_class itself, in which case we can't move
     * its pg_class row because CatalogTupleInsert/CatalogTupleUpdate might
     * not know about all the indexes yet (see reindex_relation).
     *
     * 3. Because we execute CREATE INDEX with just share lock on the parent
     * rel (to allow concurrent index creations), an ordinary update could
     * suffer a tuple-concurrently-updated failure against another CREATE
     * INDEX committing at about the same time.  We can avoid that by having
     * them both do nontransactional updates (we assume they will both be
     * trying to change the pg_class row to the same thing, so it doesn't
     * matter which goes first).
     *
     * It is safe to use a non-transactional update even though our
     * transaction could still fail before committing.  Setting relhasindex
     * true is safe even if there are no indexes (VACUUM will eventually fix
     * it), likewise for relhaspkey.  And of course the new relpages and
     * reltuples counts are correct regardless.  However, we don't want to
     * change relpages (or relallvisible) if the caller isn't providing an
     * updated reltuples count, because that would bollix the
     * reltuples/relpages ratio which is what's really important.
     */

    pg_class = heap_open(RelationRelationId, RowExclusiveLock);

    /*
     * Make a copy of the tuple to update.  Normally we use the syscache, but
     * we can't rely on that during bootstrap or while reindexing pg_class
     * itself.
     */
    if (IsBootstrapProcessingMode() ||
        ReindexIsProcessingHeap(RelationRelationId))
    {
        /* don't assume syscache will work */
        HeapScanDesc pg_class_scan;
        ScanKeyData key[1];

        ScanKeyInit(&key[0],
                    ObjectIdAttributeNumber,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(relid));

        pg_class_scan = heap_beginscan_catalog(pg_class, 1, key);
        tuple = heap_getnext(pg_class_scan, ForwardScanDirection);
        tuple = heap_copytuple(tuple);
        heap_endscan(pg_class_scan);
    }
    else
    {
        /* normal case, use syscache */
        tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
    }

    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "could not find tuple for relation %u", relid);
    rd_rel = (Form_pg_class) GETSTRUCT(tuple);

    /* Apply required updates, if any, to copied tuple */

    dirty = false;
    if (rd_rel->relhasindex != hasindex)
    {
        rd_rel->relhasindex = hasindex;
        dirty = true;
    }
    if (isprimary)
    {
        if (!rd_rel->relhaspkey)
        {
            rd_rel->relhaspkey = true;
            dirty = true;
        }
    }

    if (reltuples >= 0)
    {
        BlockNumber relpages = RelationGetNumberOfBlocks(rel);
        BlockNumber relallvisible;

        if (rd_rel->relkind != RELKIND_INDEX)
            visibilitymap_count(rel, &relallvisible, NULL);
        else                    /* don't bother for indexes */
            relallvisible = 0;

        if (rd_rel->relpages != (int32) relpages)
        {
            rd_rel->relpages = (int32) relpages;
            dirty = true;
        }
        if (rd_rel->reltuples != (float4) reltuples)
        {
            rd_rel->reltuples = (float4) reltuples;
            dirty = true;
        }
        if (rd_rel->relallvisible != (int32) relallvisible)
        {
            rd_rel->relallvisible = (int32) relallvisible;
            dirty = true;
        }
    }

    /*
     * If anything changed, write out the tuple
     */
    if (dirty)
    {
        heap_inplace_update(pg_class, tuple);
        /* the above sends a cache inval message */
    }
    else
    {
        /* no need to change tuple, but force relcache inval anyway */
        CacheInvalidateRelcacheByTuple(tuple);
    }

    heap_freetuple(tuple);

    heap_close(pg_class, RowExclusiveLock);
}


/*
 * index_build - invoke access-method-specific index build procedure
 *
 * On entry, the index's catalog entries are valid, and its physical disk
 * file has been created but is empty.  We call the AM-specific build
 * procedure to fill in the index contents.  We then update the pg_class
 * entries of the index and heap relation as needed, using statistics
 * returned by ambuild as well as data passed by the caller.
 *
 * isprimary tells whether to mark the index as a primary-key index.
 * isreindex indicates we are recreating a previously-existing index.
 *
 * Note: when reindexing an existing index, isprimary can be false even if
 * the index is a PK; it's already properly marked and need not be re-marked.
 *
 * Note: before Postgres 8.2, the passed-in heap and index Relations
 * were automatically closed by this routine.  This is no longer the case.
 * The caller opened 'em, and the caller should close 'em.
 */
void
index_build(Relation heapRelation,
            Relation indexRelation,
            IndexInfo *indexInfo,
            bool isprimary,
            bool isreindex)
{
    IndexBuildResult *stats;
    Oid         save_userid;
    int         save_sec_context;
    int         save_nestlevel;

    /*
     * sanity checks
     */
    Assert(RelationIsValid(indexRelation));
    Assert(PointerIsValid(indexRelation->rd_amroutine));
    Assert(PointerIsValid(indexRelation->rd_amroutine->ambuild));
    Assert(PointerIsValid(indexRelation->rd_amroutine->ambuildempty));

    ereport(DEBUG1,
            (errmsg("building index \"%s\" on table \"%s\"",
                    RelationGetRelationName(indexRelation),
                    RelationGetRelationName(heapRelation))));

    /*
     * Switch to the table owner's userid, so that any index functions are run
     * as that user.  Also lock down security-restricted operations and
     * arrange to make GUC variable changes local to this command.
     */
    GetUserIdAndSecContext(&save_userid, &save_sec_context);
    SetUserIdAndSecContext(heapRelation->rd_rel->relowner,
                           save_sec_context | SECURITY_RESTRICTED_OPERATION);
    save_nestlevel = NewGUCNestLevel();

    /*
     * Call the access method's build procedure
     */
    stats = indexRelation->rd_amroutine->ambuild(heapRelation, indexRelation,
                                                 indexInfo);
    Assert(PointerIsValid(stats));

    /*
     * If this is an unlogged index, we may need to write out an init fork for
     * it -- but we must first check whether one already exists.  If, for
     * example, an unlogged relation is truncated in the transaction that
     * created it, or truncated twice in a subsequent transaction, the
     * relfilenode won't change, and nothing needs to be done here.
     */
    if (indexRelation->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
        !smgrexists(indexRelation->rd_smgr, INIT_FORKNUM))
    {
        RelationOpenSmgr(indexRelation);
        smgrcreate(indexRelation->rd_smgr, INIT_FORKNUM, false);
        indexRelation->rd_amroutine->ambuildempty(indexRelation);
    }

    /*
     * If we found any potentially broken HOT chains, mark the index as not
     * being usable until the current transaction is below the event horizon.
     * See src/backend/access/heap/README.HOT for discussion.  Also set this
     * if early pruning/vacuuming is enabled for the heap relation.  While it
     * might become safe to use the index earlier based on actual cleanup
     * activity and other active transactions, the test for that would be much
     * more complex and would require some form of blocking, so keep it simple
     * and fast by just using the current transaction.
     *
     * However, when reindexing an existing index, we should do nothing here.
     * Any HOT chains that are broken with respect to the index must predate
     * the index's original creation, so there is no need to change the
     * index's usability horizon.  Moreover, we *must not* try to change the
     * index's pg_index entry while reindexing pg_index itself, and this
     * optimization nicely prevents that.  The more complex rules needed for a
     * reindex are handled separately after this function returns.
     *
     * We also need not set indcheckxmin during a concurrent index build,
     * because we won't set indisvalid true until all transactions that care
     * about the broken HOT chains or early pruning/vacuuming are gone.
     *
     * Therefore, this code path can only be taken during non-concurrent
     * CREATE INDEX.  Thus the fact that heap_update will set the pg_index
     * tuple's xmin doesn't matter, because that tuple was created in the
     * current transaction anyway.  That also means we don't need to worry
     * about any concurrent readers of the tuple; no other transaction can see
     * it yet.
     */
    if ((indexInfo->ii_BrokenHotChain || EarlyPruningEnabled(heapRelation)) &&
        !isreindex &&
        !indexInfo->ii_Concurrent)
    {
        Oid         indexId = RelationGetRelid(indexRelation);
        Relation    pg_index;
        HeapTuple   indexTuple;
        Form_pg_index indexForm;

        pg_index = heap_open(IndexRelationId, RowExclusiveLock);

        indexTuple = SearchSysCacheCopy1(INDEXRELID,
                                         ObjectIdGetDatum(indexId));
        if (!HeapTupleIsValid(indexTuple))
            elog(ERROR, "cache lookup failed for index %u", indexId);
        indexForm = (Form_pg_index) GETSTRUCT(indexTuple);

        /* If it's a new index, indcheckxmin shouldn't be set ... */
        Assert(!indexForm->indcheckxmin);

        indexForm->indcheckxmin = true;
        CatalogTupleUpdate(pg_index, &indexTuple->t_self, indexTuple);

        heap_freetuple(indexTuple);
        heap_close(pg_index, RowExclusiveLock);
    }

    /*
     * Update heap and index pg_class rows
     */
    index_update_stats(heapRelation,
                       true,
                       isprimary,
                       stats->heap_tuples);

    index_update_stats(indexRelation,
                       false,
                       false,
                       stats->index_tuples);

    /* Make the updated catalog row versions visible */
    CommandCounterIncrement();

    /*
     * If it's for an exclusion constraint, make a second pass over the heap
     * to verify that the constraint is satisfied.  We must not do this until
     * the index is fully valid.  (Broken HOT chains shouldn't matter, though;
     * see comments for IndexCheckExclusion.)
     */
    if (indexInfo->ii_ExclusionOps != NULL)
        IndexCheckExclusion(heapRelation, indexRelation, indexInfo);

    /* Roll back any GUC changes executed by index functions */
    AtEOXact_GUC(false, save_nestlevel);

    /* Restore userid and security context */
    SetUserIdAndSecContext(save_userid, save_sec_context);
}


/*
 * IndexBuildHeapScan - scan the heap relation to find tuples to be indexed
 *
 * This is called back from an access-method-specific index build procedure
 * after the AM has done whatever setup it needs.  The parent heap relation
 * is scanned to find tuples that should be entered into the index.  Each
 * such tuple is passed to the AM's callback routine, which does the right
 * things to add it to the new index.  After we return, the AM's index
 * build procedure does whatever cleanup it needs.
 *
 * The total count of heap tuples is returned.  This is for updating pg_class
 * statistics.  (It's annoying not to be able to do that here, but we want
 * to merge that update with others; see index_update_stats.)  Note that the
 * index AM itself must keep track of the number of index tuples; we don't do
 * so here because the AM might reject some of the tuples for its own reasons,
 * such as being unable to store NULLs.
 *
 * A side effect is to set indexInfo->ii_BrokenHotChain to true if we detect
 * any potentially broken HOT chains.  Currently, we set this if there are
 * any RECENTLY_DEAD or DELETE_IN_PROGRESS entries in a HOT chain, without
 * trying very hard to detect whether they're really incompatible with the
 * chain tip.
 */
double
IndexBuildHeapScan(Relation heapRelation,
                   Relation indexRelation,
                   IndexInfo *indexInfo,
                   bool allow_sync,
                   IndexBuildCallback callback,
                   void *callback_state)
{
    return IndexBuildHeapRangeScan(heapRelation, indexRelation,
                                   indexInfo, allow_sync,
                                   false,
                                   0, InvalidBlockNumber,
                                   callback, callback_state);
}

/*
 * As above, except that instead of scanning the complete heap, only the given
 * number of blocks are scanned.  Scan to end-of-rel can be signalled by
 * passing InvalidBlockNumber as numblocks.  Note that restricting the range
 * to scan cannot be done when requesting syncscan.
 *
 * When "anyvisible" mode is requested, all tuples visible to any transaction
 * are considered, including those inserted or deleted by transactions that are
 * still in progress.
 */
double
IndexBuildHeapRangeScan(Relation heapRelation,
                        Relation indexRelation,
                        IndexInfo *indexInfo,
                        bool allow_sync,
                        bool anyvisible,
                        BlockNumber start_blockno,
                        BlockNumber numblocks,
                        IndexBuildCallback callback,
                        void *callback_state)
{
    bool        is_system_catalog;
    bool        checking_uniqueness;
    HeapScanDesc scan;
    HeapTuple   heapTuple;
    Datum       values[INDEX_MAX_KEYS];
    bool        isnull[INDEX_MAX_KEYS];
    double      reltuples;
    ExprState  *predicate;
    TupleTableSlot *slot;
    EState     *estate;
    ExprContext *econtext;
    Snapshot    snapshot;
    TransactionId OldestXmin;
    BlockNumber root_blkno = InvalidBlockNumber;
    OffsetNumber root_offsets[MaxHeapTuplesPerPage];

    /*
     * sanity checks
     */
    Assert(OidIsValid(indexRelation->rd_rel->relam));

    /* Remember if it's a system catalog */
    is_system_catalog = IsSystemRelation(heapRelation);

    /* See whether we're verifying uniqueness/exclusion properties */
    checking_uniqueness = (indexInfo->ii_Unique ||
                           indexInfo->ii_ExclusionOps != NULL);

    /*
     * "Any visible" mode is not compatible with uniqueness checks; make sure
     * only one of those is requested.
     */
    Assert(!(anyvisible && checking_uniqueness));

    /*
     * Need an EState for evaluation of index expressions and partial-index
     * predicates.  Also a slot to hold the current tuple.
     */
    estate = CreateExecutorState();
    econtext = GetPerTupleExprContext(estate);
    slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRelation));

    /* Arrange for econtext's scan tuple to be the tuple under test */
    econtext->ecxt_scantuple = slot;

    /* Set up execution state for predicate, if any. */
    predicate = ExecPrepareQual(indexInfo->ii_Predicate, estate);

    /*
     * Prepare for scan of the base relation.  In a normal index build, we use
     * SnapshotAny because we must retrieve all tuples and do our own time
     * qual checks (because we have to index RECENTLY_DEAD tuples). In a
     * concurrent build, or during bootstrap, we take a regular MVCC snapshot
     * and index whatever's live according to that.
     */
    if (IsBootstrapProcessingMode() || indexInfo->ii_Concurrent)
    {
        snapshot = RegisterSnapshot(GetTransactionSnapshot());
        OldestXmin = InvalidTransactionId;  /* not used */

        /* "any visible" mode is not compatible with this */
        Assert(!anyvisible);
    }
    else
    {
        snapshot = SnapshotAny;
        /* okay to ignore lazy VACUUMs here */
        OldestXmin = GetOldestXmin(heapRelation, PROCARRAY_FLAGS_VACUUM);
    }

    scan = heap_beginscan_strat(heapRelation,   /* relation */
                                snapshot,   /* snapshot */
                                0,  /* number of keys */
                                NULL,   /* scan key */
                                true,   /* buffer access strategy OK */
                                allow_sync);    /* syncscan OK? */

    /* set our scan endpoints */
    if (!allow_sync)
        heap_setscanlimits(scan, start_blockno, numblocks);
    else
    {
        /* syncscan can only be requested on whole relation */
        Assert(start_blockno == 0);
        Assert(numblocks == InvalidBlockNumber);
    }

    reltuples = 0;

    /*
     * Scan all tuples in the base relation.
     */
    while ((heapTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
    {
        bool        tupleIsAlive;

        CHECK_FOR_INTERRUPTS();

        /*
         * When dealing with a HOT-chain of updated tuples, we want to index
         * the values of the live tuple (if any), but index it under the TID
         * of the chain's root tuple.  This approach is necessary to preserve
         * the HOT-chain structure in the heap. So we need to be able to find
         * the root item offset for every tuple that's in a HOT-chain.  When
         * first reaching a new page of the relation, call
         * heap_get_root_tuples() to build a map of root item offsets on the
         * page.
         *
         * It might look unsafe to use this information across buffer
         * lock/unlock.  However, we hold ShareLock on the table so no
         * ordinary insert/update/delete should occur; and we hold pin on the
         * buffer continuously while visiting the page, so no pruning
         * operation can occur either.
         *
         * Also, although our opinions about tuple liveness could change while
         * we scan the page (due to concurrent transaction commits/aborts),
         * the chain root locations won't, so this info doesn't need to be
         * rebuilt after waiting for another transaction.
         *
         * Note the implied assumption that there is no more than one live
         * tuple per HOT-chain --- else we could create more than one index
         * entry pointing to the same root tuple.
         */
        if (scan->rs_cblock != root_blkno)
        {
            Page        page = BufferGetPage(scan->rs_cbuf);

            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
            heap_get_root_tuples(page, root_offsets);
            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);

            root_blkno = scan->rs_cblock;
        }

        if (snapshot == SnapshotAny)
        {
            /* do our own time qual check */
            bool        indexIt;
            TransactionId xwait;

    recheck:

            /*
             * We could possibly get away with not locking the buffer here,
             * since caller should hold ShareLock on the relation, but let's
             * be conservative about it.  (This remark is still correct even
             * with HOT-pruning: our pin on the buffer prevents pruning.)
             */
            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);

            switch (HeapTupleSatisfiesVacuum(heapTuple, OldestXmin,
                                             scan->rs_cbuf))
            {
                case HEAPTUPLE_DEAD:
                    /* Definitely dead, we can ignore it */
                    indexIt = false;
                    tupleIsAlive = false;
                    break;
                case HEAPTUPLE_LIVE:
                    /* Normal case, index and unique-check it */
                    indexIt = true;
                    tupleIsAlive = true;
                    break;
                case HEAPTUPLE_RECENTLY_DEAD:

                    /*
                     * If tuple is recently deleted then we must index it
                     * anyway to preserve MVCC semantics.  (Pre-existing
                     * transactions could try to use the index after we finish
                     * building it, and may need to see such tuples.)
                     *
                     * However, if it was HOT-updated then we must only index
                     * the live tuple at the end of the HOT-chain.  Since this
                     * breaks semantics for pre-existing snapshots, mark the
                     * index as unusable for them.
                     */
                    if (HeapTupleIsHotUpdated(heapTuple))
                    {
                        indexIt = false;
                        /* mark the index as unsafe for old snapshots */
                        indexInfo->ii_BrokenHotChain = true;
                    }
                    else
                        indexIt = true;
                    /* In any case, exclude the tuple from unique-checking */
                    tupleIsAlive = false;
                    break;
                case HEAPTUPLE_INSERT_IN_PROGRESS:

                    /*
                     * In "anyvisible" mode, this tuple is visible and we
                     * don't need any further checks.
                     */
                    if (anyvisible)
                    {
                        indexIt = true;
                        tupleIsAlive = true;
                        break;
                    }

                    /*
                     * Since caller should hold ShareLock or better, normally
                     * the only way to see this is if it was inserted earlier
                     * in our own transaction.  However, it can happen in
                     * system catalogs, since we tend to release write lock
                     * before commit there.  Give a warning if neither case
                     * applies.
                     */
                    xwait = HeapTupleHeaderGetXmin(heapTuple->t_data);
                    if (!TransactionIdIsCurrentTransactionId(xwait))
                    {
                        if (!is_system_catalog)
                            elog(WARNING, "concurrent insert in progress within table \"%s\"",
                                 RelationGetRelationName(heapRelation));

                        /*
                         * If we are performing uniqueness checks, indexing
                         * such a tuple could lead to a bogus uniqueness
                         * failure.  In that case we wait for the inserting
                         * transaction to finish and check again.
                         */
                        if (checking_uniqueness)
                        {
                            /*
                             * Must drop the lock on the buffer before we wait
                             */
                            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
                            XactLockTableWait(xwait, heapRelation,
                                              &heapTuple->t_self,
                                              XLTW_InsertIndexUnique);
                            CHECK_FOR_INTERRUPTS();
                            goto recheck;
                        }
                    }

                    /*
                     * We must index such tuples, since if the index build
                     * commits then they're good.
                     */
                    indexIt = true;
                    tupleIsAlive = true;
                    break;
                case HEAPTUPLE_DELETE_IN_PROGRESS:

                    /*
                     * As with INSERT_IN_PROGRESS case, this is unexpected
                     * unless it's our own deletion or a system catalog; but
                     * in anyvisible mode, this tuple is visible.
                     */
                    if (anyvisible)
                    {
                        indexIt = true;
                        tupleIsAlive = false;
                        break;
                    }

                    xwait = HeapTupleHeaderGetUpdateXid(heapTuple->t_data);
                    if (!TransactionIdIsCurrentTransactionId(xwait))
                    {
                        if (!is_system_catalog)
                            elog(WARNING, "concurrent delete in progress within table \"%s\"",
                                 RelationGetRelationName(heapRelation));

                        /*
                         * If we are performing uniqueness checks, assuming
                         * the tuple is dead could lead to missing a
                         * uniqueness violation.  In that case we wait for the
                         * deleting transaction to finish and check again.
                         *
                         * Also, if it's a HOT-updated tuple, we should not
                         * index it but rather the live tuple at the end of
                         * the HOT-chain.  However, the deleting transaction
                         * could abort, possibly leaving this tuple as live
                         * after all, in which case it has to be indexed. The
                         * only way to know what to do is to wait for the
                         * deleting transaction to finish and check again.
                         */
                        if (checking_uniqueness ||
                            HeapTupleIsHotUpdated(heapTuple))
                        {
                            /*
                             * Must drop the lock on the buffer before we wait
                             */
                            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
                            XactLockTableWait(xwait, heapRelation,
                                              &heapTuple->t_self,
                                              XLTW_InsertIndexUnique);
                            CHECK_FOR_INTERRUPTS();
                            goto recheck;
                        }

                        /*
                         * Otherwise index it but don't check for uniqueness,
                         * the same as a RECENTLY_DEAD tuple.
                         */
                        indexIt = true;
                    }
                    else if (HeapTupleIsHotUpdated(heapTuple))
                    {
                        /*
                         * It's a HOT-updated tuple deleted by our own xact.
                         * We can assume the deletion will commit (else the
                         * index contents don't matter), so treat the same as
                         * RECENTLY_DEAD HOT-updated tuples.
                         */
                        indexIt = false;
                        /* mark the index as unsafe for old snapshots */
                        indexInfo->ii_BrokenHotChain = true;
                    }
                    else
                    {
                        /*
                         * It's a regular tuple deleted by our own xact. Index
                         * it but don't check for uniqueness, the same as a
                         * RECENTLY_DEAD tuple.
                         */
                        indexIt = true;
                    }
                    /* In any case, exclude the tuple from unique-checking */
                    tupleIsAlive = false;
                    break;
                default:
                    elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
                    indexIt = tupleIsAlive = false; /* keep compiler quiet */
                    break;
            }

            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);

            if (!indexIt)
                continue;
        }
        else
        {
            /* heap_getnext did the time qual check */
            tupleIsAlive = true;
        }

        reltuples += 1;

        MemoryContextReset(econtext->ecxt_per_tuple_memory);

        /* Set up for predicate or expression evaluation */
        ExecStoreTuple(heapTuple, slot, InvalidBuffer, false);

        /*
         * In a partial index, discard tuples that don't satisfy the
         * predicate.
         */
        if (predicate != NULL)
        {
            if (!ExecQual(predicate, econtext))
                continue;
        }

        /*
         * For the current heap tuple, extract all the attributes we use in
         * this index, and note which are null.  This also performs evaluation
         * of any expressions needed.
         */
        FormIndexDatum(indexInfo,
                       slot,
                       estate,
                       values,
                       isnull);

        /*
         * You'd think we should go ahead and build the index tuple here, but
         * some index AMs want to do further processing on the data first.  So
         * pass the values[] and isnull[] arrays, instead.
         */

        if (HeapTupleIsHeapOnly(heapTuple))
        {
            /*
             * For a heap-only tuple, pretend its TID is that of the root. See
             * src/backend/access/heap/README.HOT for discussion.
             */
            HeapTupleData rootTuple;
            OffsetNumber offnum;

            rootTuple = *heapTuple;
            offnum = ItemPointerGetOffsetNumber(&heapTuple->t_self);

            if (!OffsetNumberIsValid(root_offsets[offnum - 1]))
                elog(ERROR, "failed to find parent tuple for heap-only tuple at (%u,%u) in table \"%s\"",
                     ItemPointerGetBlockNumber(&heapTuple->t_self),
                     offnum, RelationGetRelationName(heapRelation));

            ItemPointerSetOffsetNumber(&rootTuple.t_self,
                                       root_offsets[offnum - 1]);

            /* Call the AM's callback routine to process the tuple */
            callback(indexRelation, &rootTuple, values, isnull, tupleIsAlive,
                     callback_state);
        }
        else
        {
            /* Call the AM's callback routine to process the tuple */
            callback(indexRelation, heapTuple, values, isnull, tupleIsAlive,
                     callback_state);
        }
    }

    heap_endscan(scan);

    /* we can now forget our snapshot, if set */
    if (IsBootstrapProcessingMode() || indexInfo->ii_Concurrent)
        UnregisterSnapshot(snapshot);

    ExecDropSingleTupleTableSlot(slot);

    FreeExecutorState(estate);

    /* These may have been pointing to the now-gone estate */
    indexInfo->ii_ExpressionsState = NIL;
    indexInfo->ii_PredicateState = NULL;

    return reltuples;
}


/*
 * IndexCheckExclusion - verify that a new exclusion constraint is satisfied
 *
 * When creating an exclusion constraint, we first build the index normally
 * and then rescan the heap to check for conflicts.  We assume that we only
 * need to validate tuples that are live according to an up-to-date snapshot,
 * and that these were correctly indexed even in the presence of broken HOT
 * chains.  This should be OK since we are holding at least ShareLock on the
 * table, meaning there can be no uncommitted updates from other transactions.
 * (Note: that wouldn't necessarily work for system catalogs, since many
 * operations release write lock early on the system catalogs.)
 */
static void
IndexCheckExclusion(Relation heapRelation,
                    Relation indexRelation,
                    IndexInfo *indexInfo)
{
    HeapScanDesc scan;
    HeapTuple   heapTuple;
    Datum       values[INDEX_MAX_KEYS];
    bool        isnull[INDEX_MAX_KEYS];
    ExprState  *predicate;
    TupleTableSlot *slot;
    EState     *estate;
    ExprContext *econtext;
    Snapshot    snapshot;

    /*
     * If we are reindexing the target index, mark it as no longer being
     * reindexed, to forestall an Assert in index_beginscan when we try to use
     * the index for probes.  This is OK because the index is now fully valid.
     */
    if (ReindexIsCurrentlyProcessingIndex(RelationGetRelid(indexRelation)))
        ResetReindexProcessing();

    /*
     * Need an EState for evaluation of index expressions and partial-index
     * predicates.  Also a slot to hold the current tuple.
     */
    estate = CreateExecutorState();
    econtext = GetPerTupleExprContext(estate);
    slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRelation));

    /* Arrange for econtext's scan tuple to be the tuple under test */
    econtext->ecxt_scantuple = slot;

    /* Set up execution state for predicate, if any. */
    predicate = ExecPrepareQual(indexInfo->ii_Predicate, estate);

    /*
     * Scan all live tuples in the base relation.
     */
    snapshot = RegisterSnapshot(GetLatestSnapshot());
    scan = heap_beginscan_strat(heapRelation,   /* relation */
                                snapshot,   /* snapshot */
                                0,  /* number of keys */
                                NULL,   /* scan key */
                                true,   /* buffer access strategy OK */
                                true);  /* syncscan OK */

    while ((heapTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
    {
        CHECK_FOR_INTERRUPTS();

        MemoryContextReset(econtext->ecxt_per_tuple_memory);

        /* Set up for predicate or expression evaluation */
        ExecStoreTuple(heapTuple, slot, InvalidBuffer, false);

        /*
         * In a partial index, ignore tuples that don't satisfy the predicate.
         */
        if (predicate != NULL)
        {
            if (!ExecQual(predicate, econtext))
                continue;
        }

        /*
         * Extract index column values, including computing expressions.
         */
        FormIndexDatum(indexInfo,
                       slot,
                       estate,
                       values,
                       isnull);

        /*
         * Check that this tuple has no conflicts.
         */
        check_exclusion_constraint(heapRelation,
                                   indexRelation, indexInfo,
                                   &(heapTuple->t_self), values, isnull,
                                   estate, true);
    }

    heap_endscan(scan);
    UnregisterSnapshot(snapshot);

    ExecDropSingleTupleTableSlot(slot);

    FreeExecutorState(estate);

    /* These may have been pointing to the now-gone estate */
    indexInfo->ii_ExpressionsState = NIL;
    indexInfo->ii_PredicateState = NULL;
}


/*
 * validate_index - support code for concurrent index builds
 *
 * We do a concurrent index build by first inserting the catalog entry for the
 * index via index_create(), marking it not indisready and not indisvalid.
 * Then we commit our transaction and start a new one, then we wait for all
 * transactions that could have been modifying the table to terminate.  Now
 * we know that any subsequently-started transactions will see the index and
 * honor its constraints on HOT updates; so while existing HOT-chains might
 * be broken with respect to the index, no currently live tuple will have an
 * incompatible HOT update done to it.  We now build the index normally via
 * index_build(), while holding a weak lock that allows concurrent
 * insert/update/delete.  Also, we index only tuples that are valid
 * as of the start of the scan (see IndexBuildHeapScan), whereas a normal
 * build takes care to include recently-dead tuples.  This is OK because
 * we won't mark the index valid until all transactions that might be able
 * to see those tuples are gone.  The reason for doing that is to avoid
 * bogus unique-index failures due to concurrent UPDATEs (we might see
 * different versions of the same row as being valid when we pass over them,
 * if we used HeapTupleSatisfiesVacuum).  This leaves us with an index that
 * does not contain any tuples added to the table while we built the index.
 *
 * Next, we mark the index "indisready" (but still not "indisvalid") and
 * commit the second transaction and start a third.  Again we wait for all
 * transactions that could have been modifying the table to terminate.  Now
 * we know that any subsequently-started transactions will see the index and
 * insert their new tuples into it.  We then take a new reference snapshot
 * which is passed to validate_index().  Any tuples that are valid according
 * to this snap, but are not in the index, must be added to the index.
 * (Any tuples committed live after the snap will be inserted into the
 * index by their originating transaction.  Any tuples committed dead before
 * the snap need not be indexed, because we will wait out all transactions
 * that might care about them before we mark the index valid.)
 *
 * validate_index() works by first gathering all the TIDs currently in the
 * index, using a bulkdelete callback that just stores the TIDs and doesn't
 * ever say "delete it".  (This should be faster than a plain indexscan;
 * also, not all index AMs support full-index indexscan.)  Then we sort the
 * TIDs, and finally scan the table doing a "merge join" against the TID list
 * to see which tuples are missing from the index.  Thus we will ensure that
 * all tuples valid according to the reference snapshot are in the index.
 *
 * Building a unique index this way is tricky: we might try to insert a
 * tuple that is already dead or is in process of being deleted, and we
 * mustn't have a uniqueness failure against an updated version of the same
 * row.  We could try to check the tuple to see if it's already dead and tell
 * index_insert() not to do the uniqueness check, but that still leaves us
 * with a race condition against an in-progress update.  To handle that,
 * we expect the index AM to recheck liveness of the to-be-inserted tuple
 * before it declares a uniqueness error.
 *
 * After completing validate_index(), we wait until all transactions that
 * were alive at the time of the reference snapshot are gone; this is
 * necessary to be sure there are none left with a transaction snapshot
 * older than the reference (and hence possibly able to see tuples we did
 * not index).  Then we mark the index "indisvalid" and commit.  Subsequent
 * transactions will be able to use it for queries.
 *
 * Doing two full table scans is a brute-force strategy.  We could try to be
 * cleverer, eg storing new tuples in a special area of the table (perhaps
 * making the table append-only by setting use_fsm).  However that would
 * add yet more locking issues.
 */
void
validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
{
    Relation    heapRelation,
                indexRelation;
    IndexInfo  *indexInfo;
    IndexVacuumInfo ivinfo;
    v_i_state   state;
    Oid         save_userid;
    int         save_sec_context;
    int         save_nestlevel;

    /* Open and lock the parent heap relation */
    heapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
    /* And the target index relation */
    indexRelation = index_open(indexId, RowExclusiveLock);

    /*
     * Fetch info needed for index_insert.  (You might think this should be
     * passed in from DefineIndex, but its copy is long gone due to having
     * been built in a previous transaction.)
     */
    indexInfo = BuildIndexInfo(indexRelation);

    /* mark build is concurrent just for consistency */
    indexInfo->ii_Concurrent = true;

    /*
     * Switch to the table owner's userid, so that any index functions are run
     * as that user.  Also lock down security-restricted operations and
     * arrange to make GUC variable changes local to this command.
     */
    GetUserIdAndSecContext(&save_userid, &save_sec_context);
    SetUserIdAndSecContext(heapRelation->rd_rel->relowner,
                           save_sec_context | SECURITY_RESTRICTED_OPERATION);
    save_nestlevel = NewGUCNestLevel();

    /*
     * Scan the index and gather up all the TIDs into a tuplesort object.
     */
    ivinfo.index = indexRelation;
    ivinfo.analyze_only = false;
    ivinfo.estimated_count = true;
    ivinfo.message_level = DEBUG2;
    ivinfo.num_heap_tuples = heapRelation->rd_rel->reltuples;
    ivinfo.strategy = NULL;

    /*
     * Encode TIDs as int8 values for the sort, rather than directly sorting
     * item pointers.  This can be significantly faster, primarily because TID
     * is a pass-by-reference type on all platforms, whereas int8 is
     * pass-by-value on most platforms.
     */
    state.tuplesort = tuplesort_begin_datum(INT8OID, Int8LessOperator,
                                            InvalidOid, false,
                                            maintenance_work_mem,
                                            false);
    state.htups = state.itups = state.tups_inserted = 0;

    (void) index_bulk_delete(&ivinfo, NULL,
                             validate_index_callback, (void *) &state);

    /* Execute the sort */
    tuplesort_performsort(state.tuplesort);

    /*
     * Now scan the heap and "merge" it with the index
     */
    validate_index_heapscan(heapRelation,
                            indexRelation,
                            indexInfo,
                            snapshot,
                            &state);

    /* Done with tuplesort object */
    tuplesort_end(state.tuplesort);

    elog(DEBUG2,
         "validate_index found %.0f heap tuples, %.0f index tuples; inserted %.0f missing tuples",
         state.htups, state.itups, state.tups_inserted);

    /* Roll back any GUC changes executed by index functions */
    AtEOXact_GUC(false, save_nestlevel);

    /* Restore userid and security context */
    SetUserIdAndSecContext(save_userid, save_sec_context);

    /* Close rels, but keep locks */
    index_close(indexRelation, NoLock);
    heap_close(heapRelation, NoLock);
}

/*
 * itemptr_encode - Encode ItemPointer as int64/int8
 *
 * This representation must produce values encoded as int64 that sort in the
 * same order as their corresponding original TID values would (using the
 * default int8 opclass to produce a result equivalent to the default TID
 * opclass).
 *
 * As noted in validate_index(), this can be significantly faster.
 */
static inline int64
itemptr_encode(ItemPointer itemptr)
{
    BlockNumber block = ItemPointerGetBlockNumber(itemptr);
    OffsetNumber offset = ItemPointerGetOffsetNumber(itemptr);
    int64       encoded;

    /*
     * Use the 16 least significant bits for the offset.  32 adjacent bits are
     * used for the block number.  Since remaining bits are unused, there
     * cannot be negative encoded values (We assume a two's complement
     * representation).
     */
    encoded = ((uint64) block << 16) | (uint16) offset;

    return encoded;
}

/*
 * itemptr_decode - Decode int64/int8 representation back to ItemPointer
 */
static inline void
itemptr_decode(ItemPointer itemptr, int64 encoded)
{
    BlockNumber block = (BlockNumber) (encoded >> 16);
    OffsetNumber offset = (OffsetNumber) (encoded & 0xFFFF);

    ItemPointerSet(itemptr, block, offset);
}

/*
 * validate_index_callback - bulkdelete callback to collect the index TIDs
 */
static bool
validate_index_callback(ItemPointer itemptr, void *opaque)
{
    v_i_state  *state = (v_i_state *) opaque;
    int64       encoded = itemptr_encode(itemptr);

    tuplesort_putdatum(state->tuplesort, Int64GetDatum(encoded), false);
    state->itups += 1;
    return false;               /* never actually delete anything */
}

/*
 * validate_index_heapscan - second table scan for concurrent index build
 *
 * This has much code in common with IndexBuildHeapScan, but it's enough
 * different that it seems cleaner to have two routines not one.
 */
static void
validate_index_heapscan(Relation heapRelation,
                        Relation indexRelation,
                        IndexInfo *indexInfo,
                        Snapshot snapshot,
                        v_i_state *state)
{
    HeapScanDesc scan;
    HeapTuple   heapTuple;
    Datum       values[INDEX_MAX_KEYS];
    bool        isnull[INDEX_MAX_KEYS];
    ExprState  *predicate;
    TupleTableSlot *slot;
    EState     *estate;
    ExprContext *econtext;
    BlockNumber root_blkno = InvalidBlockNumber;
    OffsetNumber root_offsets[MaxHeapTuplesPerPage];
    bool        in_index[MaxHeapTuplesPerPage];

    /* state variables for the merge */
    ItemPointer indexcursor = NULL;
    ItemPointerData decoded;
    bool        tuplesort_empty = false;

    /*
     * sanity checks
     */
    Assert(OidIsValid(indexRelation->rd_rel->relam));

    /*
     * Need an EState for evaluation of index expressions and partial-index
     * predicates.  Also a slot to hold the current tuple.
     */
    estate = CreateExecutorState();
    econtext = GetPerTupleExprContext(estate);
    slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRelation));

    /* Arrange for econtext's scan tuple to be the tuple under test */
    econtext->ecxt_scantuple = slot;

    /* Set up execution state for predicate, if any. */
    predicate = ExecPrepareQual(indexInfo->ii_Predicate, estate);

    /*
     * Prepare for scan of the base relation.  We need just those tuples
     * satisfying the passed-in reference snapshot.  We must disable syncscan
     * here, because it's critical that we read from block zero forward to
     * match the sorted TIDs.
     */
    scan = heap_beginscan_strat(heapRelation,   /* relation */
                                snapshot,   /* snapshot */
                                0,  /* number of keys */
                                NULL,   /* scan key */
                                true,   /* buffer access strategy OK */
                                false); /* syncscan not OK */

    /*
     * Scan all tuples matching the snapshot.
     */
    while ((heapTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
    {
        ItemPointer heapcursor = &heapTuple->t_self;
        ItemPointerData rootTuple;
        OffsetNumber root_offnum;

        CHECK_FOR_INTERRUPTS();

        state->htups += 1;

        /*
         * As commented in IndexBuildHeapScan, we should index heap-only
         * tuples under the TIDs of their root tuples; so when we advance onto
         * a new heap page, build a map of root item offsets on the page.
         *
         * This complicates merging against the tuplesort output: we will
         * visit the live tuples in order by their offsets, but the root
         * offsets that we need to compare against the index contents might be
         * ordered differently.  So we might have to "look back" within the
         * tuplesort output, but only within the current page.  We handle that
         * by keeping a bool array in_index[] showing all the
         * already-passed-over tuplesort output TIDs of the current page. We
         * clear that array here, when advancing onto a new heap page.
         */
        if (scan->rs_cblock != root_blkno)
        {
            Page        page = BufferGetPage(scan->rs_cbuf);

            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
            heap_get_root_tuples(page, root_offsets);
            LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);

            memset(in_index, 0, sizeof(in_index));

            root_blkno = scan->rs_cblock;
        }

        /* Convert actual tuple TID to root TID */
        rootTuple = *heapcursor;
        root_offnum = ItemPointerGetOffsetNumber(heapcursor);

        if (HeapTupleIsHeapOnly(heapTuple))
        {
            root_offnum = root_offsets[root_offnum - 1];
            if (!OffsetNumberIsValid(root_offnum))
                elog(ERROR, "failed to find parent tuple for heap-only tuple at (%u,%u) in table \"%s\"",
                     ItemPointerGetBlockNumber(heapcursor),
                     ItemPointerGetOffsetNumber(heapcursor),
                     RelationGetRelationName(heapRelation));
            ItemPointerSetOffsetNumber(&rootTuple, root_offnum);
        }

        /*
         * "merge" by skipping through the index tuples until we find or pass
         * the current root tuple.
         */
        while (!tuplesort_empty &&
               (!indexcursor ||
                ItemPointerCompare(indexcursor, &rootTuple) < 0))
        {
            Datum       ts_val;
            bool        ts_isnull;

            if (indexcursor)
            {
                /*
                 * Remember index items seen earlier on the current heap page
                 */
                if (ItemPointerGetBlockNumber(indexcursor) == root_blkno)
                    in_index[ItemPointerGetOffsetNumber(indexcursor) - 1] = true;
            }

            tuplesort_empty = !tuplesort_getdatum(state->tuplesort, true,
                                                  &ts_val, &ts_isnull, NULL);
            Assert(tuplesort_empty || !ts_isnull);
            if (!tuplesort_empty)
            {
                itemptr_decode(&decoded, DatumGetInt64(ts_val));
                indexcursor = &decoded;

                /* If int8 is pass-by-ref, free (encoded) TID Datum memory */
#ifndef USE_FLOAT8_BYVAL
                pfree(DatumGetPointer(ts_val));
#endif
            }
            else
            {
                /* Be tidy */
                indexcursor = NULL;
            }
        }

        /*
         * If the tuplesort has overshot *and* we didn't see a match earlier,
         * then this tuple is missing from the index, so insert it.
         */
        if ((tuplesort_empty ||
             ItemPointerCompare(indexcursor, &rootTuple) > 0) &&
            !in_index[root_offnum - 1])
        {
            MemoryContextReset(econtext->ecxt_per_tuple_memory);

            /* Set up for predicate or expression evaluation */
            ExecStoreTuple(heapTuple, slot, InvalidBuffer, false);

            /*
             * In a partial index, discard tuples that don't satisfy the
             * predicate.
             */
            if (predicate != NULL)
            {
                if (!ExecQual(predicate, econtext))
                    continue;
            }

            /*
             * For the current heap tuple, extract all the attributes we use
             * in this index, and note which are null.  This also performs
             * evaluation of any expressions needed.
             */
            FormIndexDatum(indexInfo,
                           slot,
                           estate,
                           values,
                           isnull);

            /*
             * You'd think we should go ahead and build the index tuple here,
             * but some index AMs want to do further processing on the data
             * first. So pass the values[] and isnull[] arrays, instead.
             */

            /*
             * If the tuple is already committed dead, you might think we
             * could suppress uniqueness checking, but this is no longer true
             * in the presence of HOT, because the insert is actually a proxy
             * for a uniqueness check on the whole HOT-chain.  That is, the
             * tuple we have here could be dead because it was already
             * HOT-updated, and if so the updating transaction will not have
             * thought it should insert index entries.  The index AM will
             * check the whole HOT-chain and correctly detect a conflict if
             * there is one.
             */

            index_insert(indexRelation,
                         values,
                         isnull,
                         &rootTuple,
                         heapRelation,
                         indexInfo->ii_Unique ?
                         UNIQUE_CHECK_YES : UNIQUE_CHECK_NO,
                         indexInfo);

            state->tups_inserted += 1;
        }
    }

    heap_endscan(scan);

    ExecDropSingleTupleTableSlot(slot);

    FreeExecutorState(estate);

    /* These may have been pointing to the now-gone estate */
    indexInfo->ii_ExpressionsState = NIL;
    indexInfo->ii_PredicateState = NULL;
}


/*
 * index_set_state_flags - adjust pg_index state flags
 *
 * This is used during CREATE/DROP INDEX CONCURRENTLY to adjust the pg_index
 * flags that denote the index's state.  Because the update is not
 * transactional and will not roll back on error, this must only be used as
 * the last step in a transaction that has not made any transactional catalog
 * updates!
 *
 * Note that heap_inplace_update does send a cache inval message for the
 * tuple, so other sessions will hear about the update as soon as we commit.
 *
 * NB: In releases prior to PostgreSQL 9.4, the use of a non-transactional
 * update here would have been unsafe; now that MVCC rules apply even for
 * system catalog scans, we could potentially use a transactional update here
 * instead.
 */
void
index_set_state_flags(Oid indexId, IndexStateFlagsAction action)
{
    Relation    pg_index;
    HeapTuple   indexTuple;
    Form_pg_index indexForm;

    /* Assert that current xact hasn't done any transactional updates */
    Assert(GetTopTransactionIdIfAny() == InvalidTransactionId);

    /* Open pg_index and fetch a writable copy of the index's tuple */
    pg_index = heap_open(IndexRelationId, RowExclusiveLock);

    indexTuple = SearchSysCacheCopy1(INDEXRELID,
                                     ObjectIdGetDatum(indexId));
    if (!HeapTupleIsValid(indexTuple))
        elog(ERROR, "cache lookup failed for index %u", indexId);
    indexForm = (Form_pg_index) GETSTRUCT(indexTuple);

    /* Perform the requested state change on the copy */
    switch (action)
    {
        case INDEX_CREATE_SET_READY:
            /* Set indisready during a CREATE INDEX CONCURRENTLY sequence */
            Assert(indexForm->indislive);
            Assert(!indexForm->indisready);
            Assert(!indexForm->indisvalid);
            indexForm->indisready = true;
            break;
        case INDEX_CREATE_SET_VALID:
            /* Set indisvalid during a CREATE INDEX CONCURRENTLY sequence */
            Assert(indexForm->indislive);
            Assert(indexForm->indisready);
            Assert(!indexForm->indisvalid);
            indexForm->indisvalid = true;
            break;
        case INDEX_DROP_CLEAR_VALID:

            /*
             * Clear indisvalid during a DROP INDEX CONCURRENTLY sequence
             *
             * If indisready == true we leave it set so the index still gets
             * maintained by active transactions.  We only need to ensure that
             * indisvalid is false.  (We don't assert that either is initially
             * true, though, since we want to be able to retry a DROP INDEX
             * CONCURRENTLY that failed partway through.)
             *
             * Note: the CLUSTER logic assumes that indisclustered cannot be
             * set on any invalid index, so clear that flag too.
             */
            indexForm->indisvalid = false;
            indexForm->indisclustered = false;
            break;
        case INDEX_DROP_SET_DEAD:

            /*
             * Clear indisready/indislive during DROP INDEX CONCURRENTLY
             *
             * We clear both indisready and indislive, because we not only
             * want to stop updates, we want to prevent sessions from touching
             * the index at all.
             */
            Assert(!indexForm->indisvalid);
            indexForm->indisready = false;
            indexForm->indislive = false;
            break;
    }

    /* ... and write it back in-place */
    heap_inplace_update(pg_index, indexTuple);

    heap_close(pg_index, RowExclusiveLock);
}


/*
 * IndexGetRelation: given an index's relation OID, get the OID of the
 * relation it is an index on.  Uses the system cache.
 */
Oid
IndexGetRelation(Oid indexId, bool missing_ok)
{
    HeapTuple   tuple;
    Form_pg_index index;
    Oid         result;

    tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexId));
    if (!HeapTupleIsValid(tuple))
    {
        if (missing_ok)
            return InvalidOid;
        elog(ERROR, "cache lookup failed for index %u", indexId);
    }
    index = (Form_pg_index) GETSTRUCT(tuple);
    Assert(index->indexrelid == indexId);

    result = index->indrelid;
    ReleaseSysCache(tuple);
    return result;
}

/*
 * reindex_index - This routine is used to recreate a single index
 */
void
reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
              int options)
{
    Relation    iRel,
                heapRelation;
    Oid         heapId;
    IndexInfo  *indexInfo;
    volatile bool skipped_constraint = false;
    PGRUsage    ru0;

    pg_rusage_init(&ru0);

    /*
     * Open and lock the parent heap relation.  ShareLock is sufficient since
     * we only need to be sure no schema or data changes are going on.
     */
    heapId = IndexGetRelation(indexId, false);
    heapRelation = heap_open(heapId, ShareLock);

    /*
     * Open the target index relation and get an exclusive lock on it, to
     * ensure that no one else is touching this particular index.
     */
    iRel = index_open(indexId, AccessExclusiveLock);

    /*
     * Don't allow reindex on temp tables of other backends ... their local
     * buffer manager is not going to cope.
     */
    if (RELATION_IS_OTHER_TEMP(iRel))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot reindex temporary tables of other sessions")));

    /*
     * Also check for active uses of the index in the current transaction; we
     * don't want to reindex underneath an open indexscan.
     */
    CheckTableNotInUse(iRel, "REINDEX INDEX");

    /*
     * All predicate locks on the index are about to be made invalid. Promote
     * them to relation locks on the heap.
     */
    TransferPredicateLocksToHeapRelation(iRel);

    PG_TRY();
    {
        /* Suppress use of the target index while rebuilding it */
        SetReindexProcessing(heapId, indexId);

        /* Fetch info needed for index_build */
        indexInfo = BuildIndexInfo(iRel);

        /* If requested, skip checking uniqueness/exclusion constraints */
        if (skip_constraint_checks)
        {
            if (indexInfo->ii_Unique || indexInfo->ii_ExclusionOps != NULL)
                skipped_constraint = true;
            indexInfo->ii_Unique = false;
            indexInfo->ii_ExclusionOps = NULL;
            indexInfo->ii_ExclusionProcs = NULL;
            indexInfo->ii_ExclusionStrats = NULL;
        }

        /* We'll build a new physical relation for the index */
        RelationSetNewRelfilenode(iRel, persistence, InvalidTransactionId,
                                  InvalidMultiXactId);

        /* Initialize the index and rebuild */
        /* Note: we do not need to re-establish pkey setting */
        index_build(heapRelation, iRel, indexInfo, false, true);
    }
    PG_CATCH();
    {
        /* Make sure flag gets cleared on error exit */
        ResetReindexProcessing();
        PG_RE_THROW();
    }
    PG_END_TRY();
    ResetReindexProcessing();

    /*
     * If the index is marked invalid/not-ready/dead (ie, it's from a failed
     * CREATE INDEX CONCURRENTLY, or a DROP INDEX CONCURRENTLY failed midway),
     * and we didn't skip a uniqueness check, we can now mark it valid.  This
     * allows REINDEX to be used to clean up in such cases.
     *
     * We can also reset indcheckxmin, because we have now done a
     * non-concurrent index build, *except* in the case where index_build
     * found some still-broken HOT chains. If it did, and we don't have to
     * change any of the other flags, we just leave indcheckxmin alone (note
     * that index_build won't have changed it, because this is a reindex).
     * This is okay and desirable because not updating the tuple leaves the
     * index's usability horizon (recorded as the tuple's xmin value) the same
     * as it was.
     *
     * But, if the index was invalid/not-ready/dead and there were broken HOT
     * chains, we had better force indcheckxmin true, because the normal
     * argument that the HOT chains couldn't conflict with the index is
     * suspect for an invalid index.  (A conflict is definitely possible if
     * the index was dead.  It probably shouldn't happen otherwise, but let's
     * be conservative.)  In this case advancing the usability horizon is
     * appropriate.
     *
     * Another reason for avoiding unnecessary updates here is that while
     * reindexing pg_index itself, we must not try to update tuples in it.
     * pg_index's indexes should always have these flags in their clean state,
     * so that won't happen.
     *
     * If early pruning/vacuuming is enabled for the heap relation, the
     * usability horizon must be advanced to the current transaction on every
     * build or rebuild.  pg_index is OK in this regard because catalog tables
     * are not subject to early cleanup.
     */
    if (!skipped_constraint)
    {
        Relation    pg_index;
        HeapTuple   indexTuple;
        Form_pg_index indexForm;
        bool        index_bad;
        bool        early_pruning_enabled = EarlyPruningEnabled(heapRelation);

        pg_index = heap_open(IndexRelationId, RowExclusiveLock);

        indexTuple = SearchSysCacheCopy1(INDEXRELID,
                                         ObjectIdGetDatum(indexId));
        if (!HeapTupleIsValid(indexTuple))
            elog(ERROR, "cache lookup failed for index %u", indexId);
        indexForm = (Form_pg_index) GETSTRUCT(indexTuple);

        index_bad = (!indexForm->indisvalid ||
                     !indexForm->indisready ||
                     !indexForm->indislive);
        if (index_bad ||
            (indexForm->indcheckxmin && !indexInfo->ii_BrokenHotChain) ||
            early_pruning_enabled)
        {
            if (!indexInfo->ii_BrokenHotChain && !early_pruning_enabled)
                indexForm->indcheckxmin = false;
            else if (index_bad || early_pruning_enabled)
                indexForm->indcheckxmin = true;
            indexForm->indisvalid = true;
            indexForm->indisready = true;
            indexForm->indislive = true;
            CatalogTupleUpdate(pg_index, &indexTuple->t_self, indexTuple);

            /*
             * Invalidate the relcache for the table, so that after we commit
             * all sessions will refresh the table's index list.  This ensures
             * that if anyone misses seeing the pg_index row during this
             * update, they'll refresh their list before attempting any update
             * on the table.
             */
            CacheInvalidateRelcache(heapRelation);
        }

        heap_close(pg_index, RowExclusiveLock);
    }

    /* Log what we did */
    if (options & REINDEXOPT_VERBOSE)
        ereport(INFO,
                (errmsg("index \"%s\" was reindexed",
                        get_rel_name(indexId)),
                 errdetail_internal("%s",
                                    pg_rusage_show(&ru0))));

    /* Close rels, but keep locks */
    index_close(iRel, NoLock);
    heap_close(heapRelation, NoLock);
}

/*
 * reindex_relation - This routine is used to recreate all indexes
 * of a relation (and optionally its toast relation too, if any).
 *
 * "flags" is a bitmask that can include any combination of these bits:
 *
 * REINDEX_REL_PROCESS_TOAST: if true, process the toast table too (if any).
 *
 * REINDEX_REL_SUPPRESS_INDEX_USE: if true, the relation was just completely
 * rebuilt by an operation such as VACUUM FULL or CLUSTER, and therefore its
 * indexes are inconsistent with it.  This makes things tricky if the relation
 * is a system catalog that we might consult during the reindexing.  To deal
 * with that case, we mark all of the indexes as pending rebuild so that they
 * won't be trusted until rebuilt.  The caller is required to call us *without*
 * having made the rebuilt table visible by doing CommandCounterIncrement;
 * we'll do CCI after having collected the index list.  (This way we can still
 * use catalog indexes while collecting the list.)
 *
 * REINDEX_REL_CHECK_CONSTRAINTS: if true, recheck unique and exclusion
 * constraint conditions, else don't.  To avoid deadlocks, VACUUM FULL or
 * CLUSTER on a system catalog must omit this flag.  REINDEX should be used to
 * rebuild an index if constraint inconsistency is suspected.  For optimal
 * performance, other callers should include the flag only after transforming
 * the data in a manner that risks a change in constraint validity.
 *
 * REINDEX_REL_FORCE_INDEXES_UNLOGGED: if true, set the persistence of the
 * rebuilt indexes to unlogged.
 *
 * REINDEX_REL_FORCE_INDEXES_PERMANENT: if true, set the persistence of the
 * rebuilt indexes to permanent.
 *
 * Returns true if any indexes were rebuilt (including toast table's index
 * when relevant).  Note that a CommandCounterIncrement will occur after each
 * index rebuild.
 */
bool
reindex_relation(Oid relid, int flags, int options)
{
    Relation    rel;
    Oid         toast_relid;
    List       *indexIds;
    bool        is_pg_class;
    bool        result;

    /*
     * Open and lock the relation.  ShareLock is sufficient since we only need
     * to prevent schema and data changes in it.  The lock level used here
     * should match ReindexTable().
     */
    rel = heap_open(relid, ShareLock);

    toast_relid = rel->rd_rel->reltoastrelid;

    /*
     * Get the list of index OIDs for this relation.  (We trust to the
     * relcache to get this with a sequential scan if ignoring system
     * indexes.)
     */
    indexIds = RelationGetIndexList(rel);

    /*
     * reindex_index will attempt to update the pg_class rows for the relation
     * and index.  If we are processing pg_class itself, we want to make sure
     * that the updates do not try to insert index entries into indexes we
     * have not processed yet.  (When we are trying to recover from corrupted
     * indexes, that could easily cause a crash.) We can accomplish this
     * because CatalogTupleInsert/CatalogTupleUpdate will use the relcache's
     * index list to know which indexes to update. We just force the index
     * list to be only the stuff we've processed.
     *
     * It is okay to not insert entries into the indexes we have not processed
     * yet because all of this is transaction-safe.  If we fail partway
     * through, the updated rows are dead and it doesn't matter whether they
     * have index entries.  Also, a new pg_class index will be created with a
     * correct entry for its own pg_class row because we do
     * RelationSetNewRelfilenode() before we do index_build().
     *
     * Note that we also clear pg_class's rd_oidindex until the loop is done,
     * so that that index can't be accessed either.  This means we cannot
     * safely generate new relation OIDs while in the loop; shouldn't be a
     * problem.
     */
    is_pg_class = (RelationGetRelid(rel) == RelationRelationId);

    /* Ensure rd_indexattr is valid; see comments for RelationSetIndexList */
    if (is_pg_class)
        (void) RelationGetIndexAttrBitmap(rel, INDEX_ATTR_BITMAP_ALL);

    PG_TRY();
    {
        List       *doneIndexes;
        ListCell   *indexId;
        char        persistence;

        if (flags & REINDEX_REL_SUPPRESS_INDEX_USE)
        {
            /* Suppress use of all the indexes until they are rebuilt */
            SetReindexPending(indexIds);

            /*
             * Make the new heap contents visible --- now things might be
             * inconsistent!
             */
            CommandCounterIncrement();
        }

        /*
         * Compute persistence of indexes: same as that of owning rel, unless
         * caller specified otherwise.
         */
        if (flags & REINDEX_REL_FORCE_INDEXES_UNLOGGED)
            persistence = RELPERSISTENCE_UNLOGGED;
        else if (flags & REINDEX_REL_FORCE_INDEXES_PERMANENT)
            persistence = RELPERSISTENCE_PERMANENT;
        else
            persistence = rel->rd_rel->relpersistence;

        /* Reindex all the indexes. */
        doneIndexes = NIL;
        foreach(indexId, indexIds)
        {
            Oid         indexOid = lfirst_oid(indexId);

            if (is_pg_class)
                RelationSetIndexList(rel, doneIndexes, InvalidOid);

            reindex_index(indexOid, !(flags & REINDEX_REL_CHECK_CONSTRAINTS),
                          persistence, options);

            CommandCounterIncrement();

            /* Index should no longer be in the pending list */
            Assert(!ReindexIsProcessingIndex(indexOid));

            if (is_pg_class)
                doneIndexes = lappend_oid(doneIndexes, indexOid);
        }
    }
    PG_CATCH();
    {
        /* Make sure list gets cleared on error exit */
        ResetReindexPending();
        PG_RE_THROW();
    }
    PG_END_TRY();
    ResetReindexPending();

    if (is_pg_class)
        RelationSetIndexList(rel, indexIds, ClassOidIndexId);

    /*
     * Close rel, but continue to hold the lock.
     */
    heap_close(rel, NoLock);

    result = (indexIds != NIL);

    /*
     * If the relation has a secondary toast rel, reindex that too while we
     * still hold the lock on the master table.
     */
    if ((flags & REINDEX_REL_PROCESS_TOAST) && OidIsValid(toast_relid))
        result |= reindex_relation(toast_relid, flags, options);

    return result;
}


/* ----------------------------------------------------------------
 *      System index reindexing support
 *
 * When we are busy reindexing a system index, this code provides support
 * for preventing catalog lookups from using that index.  We also make use
 * of this to catch attempted uses of user indexes during reindexing of
 * those indexes.
 * ----------------------------------------------------------------
 */

static Oid  currentlyReindexedHeap = InvalidOid;
static Oid  currentlyReindexedIndex = InvalidOid;
static List *pendingReindexedIndexes = NIL;

/*
 * ReindexIsProcessingHeap
 *      True if heap specified by OID is currently being reindexed.
 */
bool
ReindexIsProcessingHeap(Oid heapOid)
{
    return heapOid == currentlyReindexedHeap;
}

/*
 * ReindexIsCurrentlyProcessingIndex
 *      True if index specified by OID is currently being reindexed.
 */
static bool
ReindexIsCurrentlyProcessingIndex(Oid indexOid)
{
    return indexOid == currentlyReindexedIndex;
}

/*
 * ReindexIsProcessingIndex
 *      True if index specified by OID is currently being reindexed,
 *      or should be treated as invalid because it is awaiting reindex.
 */
bool
ReindexIsProcessingIndex(Oid indexOid)
{
    return indexOid == currentlyReindexedIndex ||
        list_member_oid(pendingReindexedIndexes, indexOid);
}

/*
 * SetReindexProcessing
 *      Set flag that specified heap/index are being reindexed.
 *
 * NB: caller must use a PG_TRY block to ensure ResetReindexProcessing is done.
 */
static void
SetReindexProcessing(Oid heapOid, Oid indexOid)
{
    Assert(OidIsValid(heapOid) && OidIsValid(indexOid));
    /* Reindexing is not re-entrant. */
    if (OidIsValid(currentlyReindexedHeap))
        elog(ERROR, "cannot reindex while reindexing");
    currentlyReindexedHeap = heapOid;
    currentlyReindexedIndex = indexOid;
    /* Index is no longer "pending" reindex. */
    RemoveReindexPending(indexOid);
}

/*
 * ResetReindexProcessing
 *      Unset reindexing status.
 */
static void
ResetReindexProcessing(void)
{
    currentlyReindexedHeap = InvalidOid;
    currentlyReindexedIndex = InvalidOid;
}

/*
 * SetReindexPending
 *      Mark the given indexes as pending reindex.
 *
 * NB: caller must use a PG_TRY block to ensure ResetReindexPending is done.
 * Also, we assume that the current memory context stays valid throughout.
 */
static void
SetReindexPending(List *indexes)
{
    /* Reindexing is not re-entrant. */
    if (pendingReindexedIndexes)
        elog(ERROR, "cannot reindex while reindexing");
    pendingReindexedIndexes = list_copy(indexes);
}

/*
 * RemoveReindexPending
 *      Remove the given index from the pending list.
 */
static void
RemoveReindexPending(Oid indexOid)
{
    pendingReindexedIndexes = list_delete_oid(pendingReindexedIndexes,
                                              indexOid);
}

/*
 * ResetReindexPending
 *      Unset reindex-pending status.
 */
static void
ResetReindexPending(void)
{
    pendingReindexedIndexes = NIL;
}