extended_stats_funcs.c

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/*-------------------------------------------------------------------------
 *
 * extended_stats_funcs.c
 *    Functions for manipulating extended statistics.
 *
 * This file includes the set of facilities required to support the direct
 * manipulations of extended statistics objects.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/statistics/extended_stats_funcs.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/heapam.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_database.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_statistic_ext_data.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "statistics/stat_utils.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
 
 
/*
 * Index of the arguments for the SQL functions.
 */
enum extended_stats_argnum
{
    RELSCHEMA_ARG = 0,
    RELNAME_ARG,
    STATSCHEMA_ARG,
    STATNAME_ARG,
    INHERITED_ARG,
    NUM_EXTENDED_STATS_ARGS,
};
 
/*
 * The argument names and type OIDs of the arguments for the SQL
 * functions.
 */
static struct StatsArgInfo extarginfo[] =
{
    [RELSCHEMA_ARG] = {"schemaname", TEXTOID},
    [RELNAME_ARG] = {"relname", TEXTOID},
    [STATSCHEMA_ARG] = {"statistics_schemaname", TEXTOID},
    [STATNAME_ARG] = {"statistics_name", TEXTOID},
    [INHERITED_ARG] = {"inherited", BOOLOID},
    [NUM_EXTENDED_STATS_ARGS] = {0},
};
 
static HeapTuple get_pg_statistic_ext(Relation pg_stext, Oid nspoid,
                                      const char *stxname);
static bool delete_pg_statistic_ext_data(Oid stxoid, bool inherited);
 
/*
 * Fetch a pg_statistic_ext row by name and namespace OID.
 */
static HeapTuple
get_pg_statistic_ext(Relation pg_stext, Oid nspoid, const char *stxname)
{
    ScanKeyData key[2];
    SysScanDesc scan;
    HeapTuple   tup;
    Oid         stxoid = InvalidOid;
 
    ScanKeyInit(&key[0],
                Anum_pg_statistic_ext_stxname,
                BTEqualStrategyNumber,
                F_NAMEEQ,
                CStringGetDatum(stxname));
    ScanKeyInit(&key[1],
                Anum_pg_statistic_ext_stxnamespace,
                BTEqualStrategyNumber,
                F_OIDEQ,
                ObjectIdGetDatum(nspoid));
 
    /*
     * Try to find matching pg_statistic_ext row.
     */
    scan = systable_beginscan(pg_stext,
                              StatisticExtNameIndexId,
                              true,
                              NULL,
                              2,
                              key);
 
    /* Lookup is based on a unique index, so we get either 0 or 1 tuple. */
    tup = systable_getnext(scan);
 
    if (HeapTupleIsValid(tup))
        stxoid = ((Form_pg_statistic_ext) GETSTRUCT(tup))->oid;
 
    systable_endscan(scan);
 
    if (!OidIsValid(stxoid))
        return NULL;
 
    return SearchSysCacheCopy1(STATEXTOID, ObjectIdGetDatum(stxoid));
}
 
/*
 * Remove an existing pg_statistic_ext_data row for a given pg_statistic_ext
 * row and "inherited" pair.
 */
static bool
delete_pg_statistic_ext_data(Oid stxoid, bool inherited)
{
    Relation    sed = table_open(StatisticExtDataRelationId, RowExclusiveLock);
    HeapTuple   oldtup;
    bool        result = false;
 
    /* Is there already a pg_statistic tuple for this attribute? */
    oldtup = SearchSysCache2(STATEXTDATASTXOID,
                             ObjectIdGetDatum(stxoid),
                             BoolGetDatum(inherited));
 
    if (HeapTupleIsValid(oldtup))
    {
        CatalogTupleDelete(sed, &oldtup->t_self);
        ReleaseSysCache(oldtup);
        result = true;
    }
 
    table_close(sed, RowExclusiveLock);
 
    CommandCounterIncrement();
 
    return result;
}
 
/*
 * Delete statistics for the given statistics object.
 */
Datum
pg_clear_extended_stats(PG_FUNCTION_ARGS)
{
    char       *relnspname;
    char       *relname;
    char       *nspname;
    Oid         nspoid;
    Oid         relid;
    char       *stxname;
    bool        inherited;
    Relation    pg_stext;
    HeapTuple   tup;
    Form_pg_statistic_ext stxform;
    Oid         locked_table = InvalidOid;
 
    /* relation arguments */
    stats_check_required_arg(fcinfo, extarginfo, RELSCHEMA_ARG);
    relnspname = TextDatumGetCString(PG_GETARG_DATUM(RELSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, RELNAME_ARG);
    relname = TextDatumGetCString(PG_GETARG_DATUM(RELNAME_ARG));
 
    /* extended statistics arguments */
    stats_check_required_arg(fcinfo, extarginfo, STATSCHEMA_ARG);
    nspname = TextDatumGetCString(PG_GETARG_DATUM(STATSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, STATNAME_ARG);
    stxname = TextDatumGetCString(PG_GETARG_DATUM(STATNAME_ARG));
    stats_check_required_arg(fcinfo, extarginfo, INHERITED_ARG);
    inherited = PG_GETARG_BOOL(INHERITED_ARG);
 
    if (RecoveryInProgress())
    {
        ereport(WARNING,
                errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                errmsg("recovery is in progress"),
                errhint("Statistics cannot be modified during recovery."));
        PG_RETURN_VOID();
    }
 
    /*
     * First open the relation where we expect to find the statistics.  This
     * is similar to relation and attribute statistics, so as ACL checks are
     * done before any locks are taken, even before any attempts related to
     * the extended stats object.
     */
    relid = RangeVarGetRelidExtended(makeRangeVar(relnspname, relname, -1),
                                     ShareUpdateExclusiveLock, 0,
                                     RangeVarCallbackForStats, &locked_table);
 
    /* Now check if the namespace of the stats object exists. */
    nspoid = get_namespace_oid(nspname, true);
    if (nspoid == InvalidOid)
    {
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find schema \"%s\"", nspname));
        PG_RETURN_VOID();
    }
 
    pg_stext = table_open(StatisticExtRelationId, RowExclusiveLock);
    tup = get_pg_statistic_ext(pg_stext, nspoid, stxname);
 
    if (!HeapTupleIsValid(tup))
    {
        table_close(pg_stext, RowExclusiveLock);
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find extended statistics object \"%s\".\"%s\"",
                       nspname, stxname));
        PG_RETURN_VOID();
    }
 
    stxform = (Form_pg_statistic_ext) GETSTRUCT(tup);
 
    /*
     * This should be consistent, based on the lock taken on the table when we
     * started.
     */
    if (stxform->stxrelid != relid)
    {
        table_close(pg_stext, RowExclusiveLock);
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not clear extended statistics object \"%s\".\"%s\": incorrect relation \"%s\".\"%s\" specified",
                       get_namespace_name(nspoid), stxname,
                       relnspname, relname));
        PG_RETURN_VOID();
    }
 
    delete_pg_statistic_ext_data(stxform->oid, inherited);
    heap_freetuple(tup);
 
    table_close(pg_stext, RowExclusiveLock);
 
    PG_RETURN_VOID();
}