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Create functions pg_set_relation_stats, pg_clear_relation_stats.
These functions are used to tweak statistics on any relation, provided that the user has MAINTAIN privilege on the relation, or is the database owner. Bump catalog version. Author: Corey Huinker Discussion: https://postgr.es/m/CADkLM=eErgzn7ECDpwFcptJKOk9SxZEk5Pot4d94eVTZsvj3gw@mail.gmail.com
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‎doc/src/sgml/func.sgml

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@@ -30135,6 +30135,100 @@ DETAIL: Make sure pg_wal_replay_wait() isn't called within a transaction with a
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</tgroup>
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</table>
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<para>
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<xref linkend="functions-admin-statsmod"/> lists functions used to
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manipulate statistics.
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<warning>
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<para>
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Changes made by these statistics manipulation functions are likely to be
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overwritten by <link linkend="autovacuum">autovacuum</link> (or manual
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<command>VACUUM</command> or <command>ANALYZE</command>) and should be
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considered temporary.
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</para>
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</warning>
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</para>
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<table id="functions-admin-statsmod">
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<title>Database Object Statistics Manipulation Functions</title>
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<tgroup cols="1">
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<thead>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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Function
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</para>
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<para>
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Description
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</para></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry role="func_table_entry">
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<para role="func_signature">
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<indexterm>
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<primary>pg_set_relation_stats</primary>
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</indexterm>
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<function>pg_set_relation_stats</function> (
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<parameter>relation</parameter> <type>regclass</type>
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<optional>, <parameter>relpages</parameter> <type>integer</type></optional>
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<optional>, <parameter>reltuples</parameter> <type>real</type></optional>
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<optional>, <parameter>relallvisible</parameter> <type>integer</type></optional> )
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Updates relation-level statistics for the given relation to the
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specified values. The parameters correspond to columns in <link
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linkend="catalog-pg-class"><structname>pg_class</structname></link>. Unspecified
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or <literal>NULL</literal> values leave the setting
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unchanged. Returns <literal>true</literal> if a change was made;
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<literal>false</literal> otherwise.
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</para>
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<para>
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Ordinarily, these statistics are collected automatically or updated
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as a part of <xref linkend="sql-vacuum"/> or <xref
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linkend="sql-analyze"/>, so it's not necessary to call this
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function. However, it may be useful when testing the effects of
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statistics on the planner to understand or anticipate plan changes.
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</para>
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<para>
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The caller must have the <literal>MAINTAIN</literal> privilege on
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the table or be the owner of the database.
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</para>
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<para>
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The value of <structfield>relpages</structfield> must be greater than
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or equal to <literal>0</literal>,
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<structfield>reltuples</structfield> must be greater than or equal to
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<literal>-1.0</literal>, and <structfield>relallvisible</structfield>
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must be greater than or equal to <literal>0</literal>.
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</para>
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</entry>
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</row>
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<row>
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<entry role="func_table_entry">
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<para role="func_signature">
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<indexterm>
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<primary>pg_clear_relation_stats</primary>
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</indexterm>
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<function>pg_clear_relation_stats</function> ( <parameter>relation</parameter> <type>regclass</type> )
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Clears table-level statistics for the given relation, as though the
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table was newly created. Returns <literal>true</literal> if a change
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was made; <literal>false</literal> otherwise.
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</para>
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<para>
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The caller must have the <literal>MAINTAIN</literal> privilege on
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the table or be the owner of the database.
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</para>
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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<xref linkend="functions-info-partition"/> lists functions that provide
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information about the structure of partitioned tables.

‎src/backend/catalog/system_functions.sql

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@@ -639,6 +639,16 @@ LANGUAGE INTERNAL
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CALLED ON NULL INPUT VOLATILE PARALLEL SAFE
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AS 'pg_stat_reset_slru';
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CREATE OR REPLACE FUNCTION
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pg_set_relation_stats(relation regclass,
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relpages integer DEFAULT NULL,
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reltuples real DEFAULT NULL,
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relallvisible integer DEFAULT NULL)
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RETURNS bool
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LANGUAGE INTERNAL
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CALLED ON NULL INPUT VOLATILE
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AS 'pg_set_relation_stats';
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--
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-- The default permissions for functions mean that anyone can execute them.
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-- A number of functions shouldn't be executable by just anyone, but rather

‎src/backend/statistics/Makefile

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@@ -16,6 +16,8 @@ OBJS = \
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dependencies.o \
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extended_stats.o \
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mcv.o \
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mvdistinct.o
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mvdistinct.o \
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relation_stats.o \
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stat_utils.o
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include $(top_srcdir)/src/backend/common.mk

‎src/backend/statistics/meson.build

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'extended_stats.c',
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'mcv.c',
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'mvdistinct.c',
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'relation_stats.c',
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'stat_utils.c'
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)

‎src/backend/statistics/relation_stats.c

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

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