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Add stxdinherit flag to pg_statistic_ext_data

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Add pg_statistic_ext_data.stxdinherit flag, so that for each extended
statistics definition we can store two versions of data - one for the
relation alone, one for the whole inheritance tree. This is analogous to
pg_statistic.stainherit, but we failed to include such flag in catalogs
for extended statistics, and we had to work around it (see commits
859b3003de, 36c4bc6e72 and 20b9fa308e).

This changes the relationship between the two catalogs storing extended
statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until
now, there was a simple 1:1 mapping - for each definition there was one
pg_statistic_ext_data row, and this row was inserted while creating the
statistics (and then updated during ANALYZE). With the stxdinherit flag,
we don't know how many rows there will be (child relations may be added
after the statistics object is defined), so there may be up to two rows.

We could make CREATE STATISTICS to always create both rows, but that
seems wasteful - without partitioning we only need stxdinherit=false
rows, and declaratively partitioned tables need only stxdinherit=true.
So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS,
and instead make that a responsibility of ANALYZE. Which is what we do
for regular statistics too.

Patch by me, with extensive improvements and fixes by Justin Pryzby.

Author: Tomas Vondra, Justin Pryzby
Reviewed-by: Tomas Vondra, Justin Pryzby
Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
This commit is contained in:
Tomas Vondra
2022-01-16 13:37:56 +01:00
parent e701bdd2f0
commit 269b532aef
19 changed files with 251 additions and 236 deletions
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146
src/backend/optimizer/util/plancat.c
View File

@@ -30,6 +30,7 @@
#include "catalog/pg_am.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_statistic_ext_data.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
@@ -1276,6 +1277,87 @@ get_relation_constraints(PlannerInfo *root,
return result;
}
/*
* Try loading data for the statistics object.
*
* We don't know if the data (specified by statOid and inh value) exist.
* The result is stored in stainfos list.
*/
static void
get_relation_statistics_worker(List **stainfos, RelOptInfo *rel,
Oid statOid, bool inh,
Bitmapset *keys, List *exprs)
{
Form_pg_statistic_ext_data dataForm;
HeapTuple dtup;
dtup = SearchSysCache2(STATEXTDATASTXOID,
ObjectIdGetDatum(statOid), BoolGetDatum(inh));
if (!HeapTupleIsValid(dtup))
return;
dataForm = (Form_pg_statistic_ext_data) GETSTRUCT(dtup);
/* add one StatisticExtInfo for each kind built */
if (statext_is_kind_built(dtup, STATS_EXT_NDISTINCT))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->inherit = dataForm->stxdinherit;
info->rel = rel;
info->kind = STATS_EXT_NDISTINCT;
info->keys = bms_copy(keys);
info->exprs = exprs;
*stainfos = lappend(*stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_DEPENDENCIES))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->inherit = dataForm->stxdinherit;
info->rel = rel;
info->kind = STATS_EXT_DEPENDENCIES;
info->keys = bms_copy(keys);
info->exprs = exprs;
*stainfos = lappend(*stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_MCV))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->inherit = dataForm->stxdinherit;
info->rel = rel;
info->kind = STATS_EXT_MCV;
info->keys = bms_copy(keys);
info->exprs = exprs;
*stainfos = lappend(*stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_EXPRESSIONS))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->inherit = dataForm->stxdinherit;
info->rel = rel;
info->kind = STATS_EXT_EXPRESSIONS;
info->keys = bms_copy(keys);
info->exprs = exprs;
*stainfos = lappend(*stainfos, info);
}
ReleaseSysCache(dtup);
}
/*
* get_relation_statistics
* Retrieve extended statistics defined on the table.
@@ -1299,7 +1381,6 @@ get_relation_statistics(RelOptInfo *rel, Relation relation)
Oid statOid = lfirst_oid(l);
Form_pg_statistic_ext staForm;
HeapTuple htup;
HeapTuple dtup;
Bitmapset *keys = NULL;
List *exprs = NIL;
int i;
@@ -1309,10 +1390,6 @@ get_relation_statistics(RelOptInfo *rel, Relation relation)
elog(ERROR, "cache lookup failed for statistics object %u", statOid);
staForm = (Form_pg_statistic_ext) GETSTRUCT(htup);
dtup = SearchSysCache1(STATEXTDATASTXOID, ObjectIdGetDatum(statOid));
if (!HeapTupleIsValid(dtup))
elog(ERROR, "cache lookup failed for statistics object %u", statOid);
/*
* First, build the array of columns covered. This is ultimately
* wasted if no stats within the object have actually been built, but
@@ -1324,6 +1401,11 @@ get_relation_statistics(RelOptInfo *rel, Relation relation)
/*
* Preprocess expressions (if any). We read the expressions, run them
* through eval_const_expressions, and fix the varnos.
*
* XXX We don't know yet if there are any data for this stats object,
* with either stxdinherit value. But it's reasonable to assume there
* is at least one of those, possibly both. So it's better to process
* keys and expressions here.
*/
{
bool isnull;
@@ -1364,61 +1446,13 @@ get_relation_statistics(RelOptInfo *rel, Relation relation)
}
}
/* add one StatisticExtInfo for each kind built */
if (statext_is_kind_built(dtup, STATS_EXT_NDISTINCT))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
/* extract statistics for possible values of stxdinherit flag */
info->statOid = statOid;
info->rel = rel;
info->kind = STATS_EXT_NDISTINCT;
info->keys = bms_copy(keys);
info->exprs = exprs;
get_relation_statistics_worker(&stainfos, rel, statOid, true, keys, exprs);
stainfos = lappend(stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_DEPENDENCIES))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->rel = rel;
info->kind = STATS_EXT_DEPENDENCIES;
info->keys = bms_copy(keys);
info->exprs = exprs;
stainfos = lappend(stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_MCV))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->rel = rel;
info->kind = STATS_EXT_MCV;
info->keys = bms_copy(keys);
info->exprs = exprs;
stainfos = lappend(stainfos, info);
}
if (statext_is_kind_built(dtup, STATS_EXT_EXPRESSIONS))
{
StatisticExtInfo *info = makeNode(StatisticExtInfo);
info->statOid = statOid;
info->rel = rel;
info->kind = STATS_EXT_EXPRESSIONS;
info->keys = bms_copy(keys);
info->exprs = exprs;
stainfos = lappend(stainfos, info);
}
get_relation_statistics_worker(&stainfos, rel, statOid, false, keys, exprs);
ReleaseSysCache(htup);
ReleaseSysCache(dtup);
bms_free(keys);
}