stat_utils.c

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/*-------------------------------------------------------------------------
 * stat_utils.c
 *
 *    PostgreSQL statistics manipulation utilities.
 *
 * Code supporting the direct manipulation of statistics.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *       src/backend/statistics/stat_utils.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/htup_details.h"
#include "access/relation.h"
#include "catalog/index.h"
#include "catalog/namespace.h"
#include "catalog/pg_class.h"
#include "catalog/pg_database.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "statistics/stat_utils.h"
#include "storage/lmgr.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
 
/*
 * Ensure that a given argument is not null.
 */
void
stats_check_required_arg(FunctionCallInfo fcinfo,
                         struct StatsArgInfo *arginfo,
                         int argnum)
{
    if (PG_ARGISNULL(argnum))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must not be null",
                        arginfo[argnum].argname)));
}
 
/*
 * Check that argument is either NULL or a one dimensional array with no
 * NULLs.
 *
 * If a problem is found, emit a WARNING, and return false. Otherwise return
 * true.
 */
bool
stats_check_arg_array(FunctionCallInfo fcinfo,
                      struct StatsArgInfo *arginfo,
                      int argnum)
{
    ArrayType  *arr;
 
    if (PG_ARGISNULL(argnum))
        return true;
 
    arr = DatumGetArrayTypeP(PG_GETARG_DATUM(argnum));
 
    if (ARR_NDIM(arr) != 1)
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must not be a multidimensional array",
                        arginfo[argnum].argname)));
        return false;
    }
 
    if (array_contains_nulls(arr))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" array must not contain null values",
                        arginfo[argnum].argname)));
        return false;
    }
 
    return true;
}
 
/*
 * Enforce parameter pairs that must be specified together (or not at all) for
 * a particular stakind, such as most_common_vals and most_common_freqs for
 * STATISTIC_KIND_MCV.
 *
 * If a problem is found, emit a WARNING, and return false. Otherwise return
 * true.
 */
bool
stats_check_arg_pair(FunctionCallInfo fcinfo,
                     struct StatsArgInfo *arginfo,
                     int argnum1, int argnum2)
{
    if (PG_ARGISNULL(argnum1) && PG_ARGISNULL(argnum2))
        return true;
 
    if (PG_ARGISNULL(argnum1) || PG_ARGISNULL(argnum2))
    {
        int         nullarg = PG_ARGISNULL(argnum1) ? argnum1 : argnum2;
        int         otherarg = PG_ARGISNULL(argnum1) ? argnum2 : argnum1;
 
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must be specified when argument \"%s\" is specified",
                        arginfo[nullarg].argname,
                        arginfo[otherarg].argname)));
 
        return false;
    }
 
    return true;
}
 
/*
 * A role has privileges to set statistics on the relation if any of the
 * following are true:
 *   - the role owns the current database and the relation is not shared
 *   - the role has the MAINTAIN privilege on the relation
 */
void
RangeVarCallbackForStats(const RangeVar *relation,
                         Oid relId, Oid oldRelId, void *arg)
{
    Oid        *locked_oid = (Oid *) arg;
    Oid         table_oid = relId;
    HeapTuple   tuple;
    Form_pg_class form;
    char        relkind;
 
    /*
     * If we previously locked some other index's heap, and the name we're
     * looking up no longer refers to that relation, release the now-useless
     * lock.
     */
    if (relId != oldRelId && OidIsValid(*locked_oid))
    {
        UnlockRelationOid(*locked_oid, ShareUpdateExclusiveLock);
        *locked_oid = InvalidOid;
    }
 
    /* If the relation does not exist, there's nothing more to do. */
    if (!OidIsValid(relId))
        return;
 
    /* If the relation does exist, check whether it's an index. */
    relkind = get_rel_relkind(relId);
    if (relkind == RELKIND_INDEX ||
        relkind == RELKIND_PARTITIONED_INDEX)
        table_oid = IndexGetRelation(relId, false);
 
    /*
     * If retrying yields the same OID, there are a couple of extremely
     * unlikely scenarios we need to handle.
     */
    if (relId == oldRelId)
    {
        /*
         * If a previous lookup found an index, but the current lookup did
         * not, the index was dropped and the OID was reused for something
         * else between lookups.  In theory, we could simply drop our lock on
         * the index's parent table and proceed, but in the interest of
         * avoiding complexity, we just error.
         */
        if (table_oid == relId && OidIsValid(*locked_oid))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("index \"%s\" was concurrently dropped",
                            relation->relname)));
 
        /*
         * If the current lookup found an index but a previous lookup either
         * did not find an index or found one with a different parent
         * relation, the relation was dropped and the OID was reused for an
         * index between lookups.  RangeVarGetRelidExtended() will have
         * already locked the index at this point, so we can't just lock the
         * newly discovered parent table OID without risking deadlock.  As
         * above, we just error in this case.
         */
        if (table_oid != relId && table_oid != *locked_oid)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("index \"%s\" was concurrently created",
                            relation->relname)));
    }
 
    tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(table_oid));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for OID %u", table_oid);
    form = (Form_pg_class) GETSTRUCT(tuple);
 
    /* the relkinds that can be used with ANALYZE */
    switch (form->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_MATVIEW:
        case RELKIND_FOREIGN_TABLE:
        case RELKIND_PARTITIONED_TABLE:
            break;
        default:
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("cannot modify statistics for relation \"%s\"",
                            NameStr(form->relname)),
                     errdetail_relkind_not_supported(form->relkind)));
    }
 
    if (form->relisshared)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot modify statistics for shared relation")));
 
    /* Check permissions */
    if (!object_ownercheck(DatabaseRelationId, MyDatabaseId, GetUserId()))
    {
        AclResult   aclresult = pg_class_aclcheck(table_oid,
                                                  GetUserId(),
                                                  ACL_MAINTAIN);
 
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult,
                           get_relkind_objtype(form->relkind),
                           NameStr(form->relname));
    }
 
    ReleaseSysCache(tuple);
 
    /* Lock heap before index to avoid deadlock. */
    if (relId != oldRelId && table_oid != relId)
    {
        LockRelationOid(table_oid, ShareUpdateExclusiveLock);
        *locked_oid = table_oid;
    }
}
 
 
/*
 * Find the argument number for the given argument name, returning -1 if not
 * found.
 */
static int
get_arg_by_name(const char *argname, struct StatsArgInfo *arginfo)
{
    int         argnum;
 
    for (argnum = 0; arginfo[argnum].argname != NULL; argnum++)
        if (pg_strcasecmp(argname, arginfo[argnum].argname) == 0)
            return argnum;
 
    ereport(WARNING,
            (errmsg("unrecognized argument name: \"%s\"", argname)));
 
    return -1;
}
 
/*
 * Ensure that a given argument matched the expected type.
 */
static bool
stats_check_arg_type(const char *argname, Oid argtype, Oid expectedtype)
{
    if (argtype != expectedtype)
    {
        ereport(WARNING,
                (errmsg("argument \"%s\" has type %s, expected type %s",
                        argname, format_type_be(argtype),
                        format_type_be(expectedtype))));
        return false;
    }
 
    return true;
}
 
/*
 * Translate variadic argument pairs from 'pairs_fcinfo' into a
 * 'positional_fcinfo' appropriate for calling relation_statistics_update() or
 * attribute_statistics_update() with positional arguments.
 *
 * Caller should have already initialized positional_fcinfo with a size
 * appropriate for calling the intended positional function, and arginfo
 * should also match the intended positional function.
 */
bool
stats_fill_fcinfo_from_arg_pairs(FunctionCallInfo pairs_fcinfo,
                                 FunctionCallInfo positional_fcinfo,
                                 struct StatsArgInfo *arginfo)
{
    Datum      *args;
    bool       *argnulls;
    Oid        *types;
    int         nargs;
    bool        result = true;
 
    /* clear positional args */
    for (int i = 0; arginfo[i].argname != NULL; i++)
    {
        positional_fcinfo->args[i].value = (Datum) 0;
        positional_fcinfo->args[i].isnull = true;
    }
 
    nargs = extract_variadic_args(pairs_fcinfo, 0, true,
                                  &args, &types, &argnulls);
 
    if (nargs % 2 != 0)
        ereport(ERROR,
                errmsg("variadic arguments must be name/value pairs"),
                errhint("Provide an even number of variadic arguments that can be divided into pairs."));
 
    /*
     * For each argument name/value pair, find corresponding positional
     * argument for the argument name, and assign the argument value to
     * positional_fcinfo.
     */
    for (int i = 0; i < nargs; i += 2)
    {
        int         argnum;
        char       *argname;
 
        if (argnulls[i])
            ereport(ERROR,
                    (errmsg("name at variadic position %d is null", i + 1)));
 
        if (types[i] != TEXTOID)
            ereport(ERROR,
                    (errmsg("name at variadic position %d has type %s, expected type %s",
                            i + 1, format_type_be(types[i]),
                            format_type_be(TEXTOID))));
 
        if (argnulls[i + 1])
            continue;
 
        argname = TextDatumGetCString(args[i]);
 
        /*
         * The 'version' argument is a special case, not handled by arginfo
         * because it's not a valid positional argument.
         *
         * For now, 'version' is accepted but ignored. In the future it can be
         * used to interpret older statistics properly.
         */
        if (pg_strcasecmp(argname, "version") == 0)
            continue;
 
        argnum = get_arg_by_name(argname, arginfo);
 
        if (argnum < 0 || !stats_check_arg_type(argname, types[i + 1],
                                                arginfo[argnum].argtype))
        {
            result = false;
            continue;
        }
 
        positional_fcinfo->args[argnum].value = args[i + 1];
        positional_fcinfo->args[argnum].isnull = false;
    }
 
    return result;
}