relation_stats.c

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/*-------------------------------------------------------------------------
 * relation_stats.c
 *
 *    PostgreSQL relation statistics manipulation
 *
 * Code supporting the direct import of relation statistics, similar to
 * what is done by the ANALYZE command.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *       src/backend/statistics/relation_stats.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/heapam.h"
#include "catalog/indexing.h"
#include "statistics/stat_utils.h"
#include "utils/fmgrprotos.h"
#include "utils/syscache.h"
 
#define DEFAULT_RELPAGES Int32GetDatum(0)
#define DEFAULT_RELTUPLES Float4GetDatum(-1.0)
#define DEFAULT_RELALLVISIBLE Int32GetDatum(0)
 
/*
 * Positional argument numbers, names, and types for
 * relation_statistics_update().
 */
 
enum relation_stats_argnum
{
    RELATION_ARG = 0,
    RELPAGES_ARG,
    RELTUPLES_ARG,
    RELALLVISIBLE_ARG,
    NUM_RELATION_STATS_ARGS
};
 
static struct StatsArgInfo relarginfo[] =
{
    [RELATION_ARG] = {"relation", REGCLASSOID},
    [RELPAGES_ARG] = {"relpages", INT4OID},
    [RELTUPLES_ARG] = {"reltuples", FLOAT4OID},
    [RELALLVISIBLE_ARG] = {"relallvisible", INT4OID},
    [NUM_RELATION_STATS_ARGS] = {0}
};
 
static bool relation_statistics_update(FunctionCallInfo fcinfo, int elevel);
 
/*
 * Internal function for modifying statistics for a relation.
 */
static bool
relation_statistics_update(FunctionCallInfo fcinfo, int elevel)
{
    Oid         reloid;
    Relation    crel;
    HeapTuple   ctup;
    Form_pg_class pgcform;
    int         replaces[3] = {0};
    Datum       values[3] = {0};
    bool        nulls[3] = {0};
    int         ncols = 0;
    TupleDesc   tupdesc;
    HeapTuple   newtup;
 
 
    stats_check_required_arg(fcinfo, relarginfo, RELATION_ARG);
    reloid = PG_GETARG_OID(RELATION_ARG);
 
    stats_lock_check_privileges(reloid);
 
    /*
     * Take RowExclusiveLock on pg_class, consistent with
     * vac_update_relstats().
     */
    crel = table_open(RelationRelationId, RowExclusiveLock);
 
    tupdesc = RelationGetDescr(crel);
    ctup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(reloid));
    if (!HeapTupleIsValid(ctup))
    {
        ereport(elevel,
                (errcode(ERRCODE_OBJECT_IN_USE),
                 errmsg("pg_class entry for relid %u not found", reloid)));
        table_close(crel, RowExclusiveLock);
        return false;
    }
 
    pgcform = (Form_pg_class) GETSTRUCT(ctup);
 
    /* relpages */
    if (!PG_ARGISNULL(RELPAGES_ARG))
    {
        int32       relpages = PG_GETARG_INT32(RELPAGES_ARG);
 
        /*
         * Partitioned tables may have relpages=-1. Note: for relations with
         * no storage, relpages=-1 is not used consistently, but must be
         * supported here.
         */
        if (relpages < -1)
        {
            ereport(elevel,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("relpages cannot be < -1")));
            table_close(crel, RowExclusiveLock);
            return false;
        }
 
        if (relpages != pgcform->relpages)
        {
            replaces[ncols] = Anum_pg_class_relpages;
            values[ncols] = Int32GetDatum(relpages);
            ncols++;
        }
    }
 
    if (!PG_ARGISNULL(RELTUPLES_ARG))
    {
        float       reltuples = PG_GETARG_FLOAT4(RELTUPLES_ARG);
 
        if (reltuples < -1.0)
        {
            ereport(elevel,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("reltuples cannot be < -1.0")));
            table_close(crel, RowExclusiveLock);
            return false;
        }
 
        if (reltuples != pgcform->reltuples)
        {
            replaces[ncols] = Anum_pg_class_reltuples;
            values[ncols] = Float4GetDatum(reltuples);
            ncols++;
        }
    }
 
    if (!PG_ARGISNULL(RELALLVISIBLE_ARG))
    {
        int32       relallvisible = PG_GETARG_INT32(RELALLVISIBLE_ARG);
 
        if (relallvisible < 0)
        {
            ereport(elevel,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("relallvisible cannot be < 0")));
            table_close(crel, RowExclusiveLock);
            return false;
        }
 
        if (relallvisible != pgcform->relallvisible)
        {
            replaces[ncols] = Anum_pg_class_relallvisible;
            values[ncols] = Int32GetDatum(relallvisible);
            ncols++;
        }
    }
 
    /* only update pg_class if there is a meaningful change */
    if (ncols == 0)
    {
        table_close(crel, RowExclusiveLock);
        return false;
    }
 
    newtup = heap_modify_tuple_by_cols(ctup, tupdesc, ncols, replaces, values,
                                       nulls);
 
    CatalogTupleUpdate(crel, &newtup->t_self, newtup);
    heap_freetuple(newtup);
 
    /* release the lock, consistent with vac_update_relstats() */
    table_close(crel, RowExclusiveLock);
 
    return true;
}
 
/*
 * Set statistics for a given pg_class entry.
 */
Datum
pg_set_relation_stats(PG_FUNCTION_ARGS)
{
    relation_statistics_update(fcinfo, ERROR);
    PG_RETURN_VOID();
}
 
/*
 * Clear statistics for a given pg_class entry; that is, set back to initial
 * stats for a newly-created table.
 */
Datum
pg_clear_relation_stats(PG_FUNCTION_ARGS)
{
    LOCAL_FCINFO(newfcinfo, 4);
 
    InitFunctionCallInfoData(*newfcinfo, NULL, 4, InvalidOid, NULL, NULL);
 
    newfcinfo->args[0].value = PG_GETARG_OID(0);
    newfcinfo->args[0].isnull = PG_ARGISNULL(0);
    newfcinfo->args[1].value = DEFAULT_RELPAGES;
    newfcinfo->args[1].isnull = false;
    newfcinfo->args[2].value = DEFAULT_RELTUPLES;
    newfcinfo->args[2].isnull = false;
    newfcinfo->args[3].value = DEFAULT_RELALLVISIBLE;
    newfcinfo->args[3].isnull = false;
 
    relation_statistics_update(newfcinfo, ERROR);
    PG_RETURN_VOID();
}