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extstats_extra.c
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extstats_extra.c
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/*-------------------------------------------------------------------------
*
* extstats_extra.c
* Extra code to operate with extended statistics. Should correspond to any
* changes in extended_stats.c
* Copyright (c) 2023-2024 Andrei Lepikhov
*
* This software may be modified and distributed under the terms
* of the MIT license. See the LICENSE file for details.
*
* IDENTIFICATION
* contrib/pg_sindex_stats/extstats_extra.c
*
*-------------------------------------------------------------------------
*/
#include "pg_index_stats.h"
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_type.h"
#include "commands/comment.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
typedef struct StatExtEntry
{
Oid statOid; /* OID of pg_statistic_ext entry */
char *schema; /* statistics object's schema */
char *name; /* statistics object's name */
Bitmapset *columns; /* attribute numbers covered by the object */
List *types; /* 'char' list of enabled statistics kinds */
List *exprs; /* expressions */
} StatExtEntry;
/* Comparison result of existed and candidate statistics */
#define CMPTYPE_DEFMATCH (1) /* Equal definitions (need to check stat types) */
#define CMPTYPE_INCLUDES (2) /* Definition of the stored covers incoming one */
#define CMPTYPE_INCLUDED (3) /* Definition of the stored is covered by definition of incoming one */
#define CMPTYPE_INTERCEPT (4) /* Both definitions have some unique elements */
#define CMPTYPE_NONE (5) /* Nothing in common */
typedef struct StatAnalyzeResult
{
int8 cmptype;
bool auto_generated; /* Generated by this extension? */
Bitmapset *columns_matched;
Bitmapset *columns_missed;
Bitmapset *columns_extra;
List *exprs_matched;
List *exprs_missed;
List *exprs_extra;
Bitmapset *stat_matched;
Bitmapset *stat_missed;
StatExtEntry *ref;
} StatAnalyzeResult;
/*
* Extract auto-generated statistics
*/
/* Be careful with versions */
#if PG_VERSION_NUM < 170000
static List *
fetch_statentries_for_relation(Relation pg_statext, Oid relid)
{
SysScanDesc scan;
ScanKeyData skey;
HeapTuple htup;
List *result = NIL;
/*
* Prepare to scan pg_statistic_ext for entries having stxrelid = this
* rel.
*/
ScanKeyInit(&skey,
Anum_pg_statistic_ext_stxrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(relid));
scan = systable_beginscan(pg_statext, StatisticExtRelidIndexId, true,
NULL, 1, &skey);
while (HeapTupleIsValid(htup = systable_getnext(scan)))
{
StatExtEntry *entry;
Datum datum;
bool isnull;
int i;
ArrayType *arr;
char *enabled;
Form_pg_statistic_ext staForm;
List *exprs = NIL;
entry = palloc0(sizeof(StatExtEntry));
staForm = (Form_pg_statistic_ext) GETSTRUCT(htup);
entry->statOid = staForm->oid;
entry->schema = get_namespace_name(staForm->stxnamespace);
entry->name = pstrdup(NameStr(staForm->stxname));
for (i = 0; i < staForm->stxkeys.dim1; i++)
{
entry->columns = bms_add_member(entry->columns,
staForm->stxkeys.values[i]);
}
/* decode the stxkind char array into a list of chars */
datum = SysCacheGetAttrNotNull(STATEXTOID, htup,
Anum_pg_statistic_ext_stxkind);
arr = DatumGetArrayTypeP(datum);
if (ARR_NDIM(arr) != 1 ||
ARR_HASNULL(arr) ||
ARR_ELEMTYPE(arr) != CHAROID)
elog(ERROR, "stxkind is not a 1-D char array");
enabled = (char *) ARR_DATA_PTR(arr);
for (i = 0; i < ARR_DIMS(arr)[0]; i++)
{
Assert((enabled[i] == STATS_EXT_NDISTINCT) ||
(enabled[i] == STATS_EXT_DEPENDENCIES) ||
(enabled[i] == STATS_EXT_MCV) ||
(enabled[i] == STATS_EXT_EXPRESSIONS));
entry->types = lappend_int(entry->types, (int) enabled[i]);
}
/* decode expression (if any) */
datum = SysCacheGetAttr(STATEXTOID, htup,
Anum_pg_statistic_ext_stxexprs, &isnull);
if (!isnull)
{
char *exprsString;
exprsString = TextDatumGetCString(datum);
exprs = (List *) stringToNode(exprsString);
pfree(exprsString);
/*
* Run the expressions through eval_const_expressions. This is not
* just an optimization, but is necessary, because the planner
* will be comparing them to similarly-processed qual clauses, and
* may fail to detect valid matches without this. We must not use
* canonicalize_qual, however, since these aren't qual
* expressions.
*/
exprs = (List *) eval_const_expressions(NULL, (Node *) exprs);
/* May as well fix opfuncids too */
fix_opfuncids((Node *) exprs);
}
entry->exprs = exprs;
result = lappend(result, entry);
}
systable_endscan(scan);
return result;
}
#endif
/*
* Pass through all extended statistics on the table.
* Analyse intersection between candidate statistics and existed one.
* Return list containing result of the analysis and links to specific entries.
* Feel free to implement additional routines to make decisions on new
* statistics and their fulfillment.
*/
List * /* of StatAnalyzeResult */
analyze_relation_statistics(Oid heapOid, Bitmapset *columns, List *exprs)
{
Relation pg_stext;
List *statslist;
ListCell *lc;
StatAnalyzeResult *result;
List *resList = NIL;
List *tmp_exprs;
/* Extract all extended statistics on the relation */
pg_stext = table_open(StatisticExtRelationId, AccessShareLock);
statslist = fetch_statentries_for_relation(pg_stext, heapOid);
table_close(pg_stext, AccessShareLock);
/* Lookup for duplicated statistics */
foreach(lc, statslist)
{
StatExtEntry *entry = (StatExtEntry *) lfirst(lc);
ListCell *lc1;
char *stxcomment;
/* Zeroing the struct on allocation to avoid annoying initializations */
result = palloc0(sizeof(StatAnalyzeResult));
/* Save link to statistics entry */
result->ref = entry;
/* Mark custom statistics has made by an user manually */
stxcomment = GetComment(entry->statOid, StatisticExtRelationId, 0);
if (stxcomment != NULL &&
strstr(stxcomment, MODULE_NAME" - ") != NULL)
result->auto_generated = true;
/*
* Compare columns of already existed and candidate
* (induced by index creation) statistics
*/
result->columns_matched = bms_intersect(columns, entry->columns);
result->columns_missed = bms_difference(columns, entry->columns);
result->columns_extra = bms_difference(entry->columns, columns);
Assert(bms_num_members(result->columns_matched) +
bms_num_members(result->columns_missed) +
bms_num_members(result->columns_extra) ==
bms_num_members(bms_union(columns, entry->columns)));
tmp_exprs = list_copy(entry->exprs);
/*
* Do the same comparison for the expressions - a bit more heavy
* operation
*/
foreach (lc1, exprs)
{
StatsElem *elem = (StatsElem *) lfirst(lc1);
Node *expr1 = elem->expr;
Node *expr2 = NULL;
ListCell *lc2;
bool found = false;
if (expr1 == NULL)
/* It is a column, not an expression */
continue;
foreach (lc2, tmp_exprs)
{
expr2 = (Node *) lfirst(lc2);
/* Don't wait NULL expression for stored statistics */
Assert(expr2 != NULL);
if (!equal(expr1, expr2))
continue;
/* We found match. Don't need to pass further. */
found = true;
break;
}
if (found)
{
Assert(expr2 != NULL);
tmp_exprs = list_delete_ptr(tmp_exprs, expr2);
result->exprs_matched = lappend(result->exprs_matched, expr1);
}
else
/* Candidate column didn't find in the existed statistics */
result->exprs_missed = lappend(result->exprs_missed, expr1);
}
/*
* Expressions, which weren't matched survive and should be stored as
* 'extra' expressions.
*/
result->exprs_extra = tmp_exprs;
/* Now we can define relation between both statistics definitions */
if (bms_is_empty(result->columns_matched) && result->exprs_matched == NIL)
result->cmptype = CMPTYPE_NONE;
/* Definitions have some common elements. Analyze further */
else if ((result->exprs_missed != NULL || !bms_is_empty(result->columns_missed)) &&
(result->exprs_extra != NULL || !bms_is_empty(result->columns_extra)))
result->cmptype = CMPTYPE_INTERCEPT;
else if ((result->exprs_missed != NULL || !bms_is_empty(result->columns_missed)) &&
(result->exprs_extra == NULL || bms_is_empty(result->columns_extra)))
result->cmptype = CMPTYPE_INCLUDED;
else if ((result->exprs_missed == NULL || bms_is_empty(result->columns_missed)) &&
(result->exprs_extra != NULL || !bms_is_empty(result->columns_extra)))
result->cmptype = CMPTYPE_INCLUDES;
else if ((result->exprs_missed == NULL && bms_is_empty(result->columns_missed)) &&
(result->exprs_extra == NULL && bms_is_empty(result->columns_extra)))
result->cmptype = CMPTYPE_DEFMATCH;
else
elog(PANIC, "Help! I've made a coding blunder!");
resList = lappend(resList, result);
/* Identify types of statistics in the entry */
result->stat_missed = bms_add_member(result->stat_missed, (int) STATS_EXT_NDISTINCT);
result->stat_missed = bms_add_member(result->stat_missed, (int) STATS_EXT_DEPENDENCIES);
result->stat_missed = bms_add_member(result->stat_missed, (int) STATS_EXT_MCV);
result->stat_missed = bms_add_member(result->stat_missed, (int) STATS_EXT_EXPRESSIONS);
foreach(lc1, entry->types)
{
char t = (char) lfirst_int(lc1);
Assert(bms_is_member((int) t, result->stat_missed));
if (t == STATS_EXT_EXPRESSIONS)
/* TODO: elaborate logic by taking into account expression stats */
continue;
result->stat_matched = bms_add_member(result->stat_matched, (int) t);
}
result->stat_missed = bms_del_members(result->stat_missed, result->stat_matched);
result->stat_missed = bms_del_member(result->stat_missed, (int) STATS_EXT_EXPRESSIONS);
}
list_free(statslist);
return resList;
}
Bitmapset *
check_duplicated(List *statList, int32 stat_types)
{
ListCell *lc;
Bitmapset *missed = NULL;
if (stat_types & STAT_NDISTINCT)
missed = bms_add_member(missed, (int) STATS_EXT_NDISTINCT);
if (stat_types & STAT_MCV)
missed = bms_add_member(missed, (int) STATS_EXT_MCV);
if (stat_types & STAT_DEPENDENCIES)
missed = bms_add_member(missed, (int) STATS_EXT_DEPENDENCIES);
foreach (lc, statList)
{
StatAnalyzeResult *stat = (StatAnalyzeResult *) lfirst(lc);
if (stat->cmptype == CMPTYPE_DEFMATCH)
{
/*
* Stat stored contains the same definition. Exclude from the newly
* created statistics already existed fields.
*/
missed = bms_del_members(missed, stat->stat_matched);
elog(DEBUG2, "Duplicated statistic definition, but absent of something: distinct: %d, mcv: %d, deps: %d",
bms_is_member((int) STATS_EXT_NDISTINCT, missed),
bms_is_member((int) STATS_EXT_MCV, missed),
bms_is_member((int) STATS_EXT_DEPENDENCIES, missed));
}
}
return missed;
}