mirror of
https://github.com/postgres/postgres.git
synced 2025-05-11 05:41:32 +03:00
c676e659b2
When picking the best extended statistics object for a list of clauses, it's not enough to look at attnums extracted from the clause list as a whole. Consider for example this query with OR clauses: SELECT * FROM t WHERE (t.a = 1) OR (t.b = 1) OR (t.c = 1) with a statistics defined on columns (a,b). Relying on attnums extracted from the whole OR clause, we'd consider the statistics usable. That does not work, as we see the conditions as a single OR-clause, referencing an attribute not covered by the statistic, leading to empty list of clauses to be estimated using the statistics and an assert failure. This changes choose_best_statistics to check which clauses are actually covered, and only using attributes from the fully covered ones. For the previous example this means the statistics object will not be considered as compatible with the OR-clause. Backpatch to 12, where MCVs were introduced. The issue does not affect older versions because functional dependencies don't handle OR clauses. Author: Tomas Vondra Reviewed-by: Dean Rasheed Reported-By: Manuel Rigger Discussion: https://postgr.es/m/CA+u7OA7H5rcE2=8f263w4NZD6ipO_XOrYB816nuLXbmSTH9pQQ@mail.gmail.com Backpatch-through: 12
126 lines
4.4 KiB
C
126 lines
4.4 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* statistics.h
|
|
* Extended statistics and selectivity estimation functions.
|
|
*
|
|
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* src/include/statistics/statistics.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef STATISTICS_H
|
|
#define STATISTICS_H
|
|
|
|
#include "commands/vacuum.h"
|
|
#include "nodes/pathnodes.h"
|
|
|
|
#define STATS_MAX_DIMENSIONS 8 /* max number of attributes */
|
|
|
|
/* Multivariate distinct coefficients */
|
|
#define STATS_NDISTINCT_MAGIC 0xA352BFA4 /* struct identifier */
|
|
#define STATS_NDISTINCT_TYPE_BASIC 1 /* struct version */
|
|
|
|
/* MVNDistinctItem represents a single combination of columns */
|
|
typedef struct MVNDistinctItem
|
|
{
|
|
double ndistinct; /* ndistinct value for this combination */
|
|
Bitmapset *attrs; /* attr numbers of items */
|
|
} MVNDistinctItem;
|
|
|
|
/* A MVNDistinct object, comprising all possible combinations of columns */
|
|
typedef struct MVNDistinct
|
|
{
|
|
uint32 magic; /* magic constant marker */
|
|
uint32 type; /* type of ndistinct (BASIC) */
|
|
uint32 nitems; /* number of items in the statistic */
|
|
MVNDistinctItem items[FLEXIBLE_ARRAY_MEMBER];
|
|
} MVNDistinct;
|
|
|
|
/* Multivariate functional dependencies */
|
|
#define STATS_DEPS_MAGIC 0xB4549A2C /* marks serialized bytea */
|
|
#define STATS_DEPS_TYPE_BASIC 1 /* basic dependencies type */
|
|
|
|
/*
|
|
* Functional dependencies, tracking column-level relationships (values
|
|
* in one column determine values in another one).
|
|
*/
|
|
typedef struct MVDependency
|
|
{
|
|
double degree; /* degree of validity (0-1) */
|
|
AttrNumber nattributes; /* number of attributes */
|
|
AttrNumber attributes[FLEXIBLE_ARRAY_MEMBER]; /* attribute numbers */
|
|
} MVDependency;
|
|
|
|
typedef struct MVDependencies
|
|
{
|
|
uint32 magic; /* magic constant marker */
|
|
uint32 type; /* type of MV Dependencies (BASIC) */
|
|
uint32 ndeps; /* number of dependencies */
|
|
MVDependency *deps[FLEXIBLE_ARRAY_MEMBER]; /* dependencies */
|
|
} MVDependencies;
|
|
|
|
/* used to flag stats serialized to bytea */
|
|
#define STATS_MCV_MAGIC 0xE1A651C2 /* marks serialized bytea */
|
|
#define STATS_MCV_TYPE_BASIC 1 /* basic MCV list type */
|
|
|
|
/* max items in MCV list (should be equal to max default_statistics_target) */
|
|
#define STATS_MCVLIST_MAX_ITEMS 10000
|
|
|
|
/*
|
|
* Multivariate MCV (most-common value) lists
|
|
*
|
|
* A straightforward extension of MCV items - i.e. a list (array) of
|
|
* combinations of attribute values, together with a frequency and null flags.
|
|
*/
|
|
typedef struct MCVItem
|
|
{
|
|
double frequency; /* frequency of this combination */
|
|
double base_frequency; /* frequency if independent */
|
|
bool *isnull; /* NULL flags */
|
|
Datum *values; /* item values */
|
|
} MCVItem;
|
|
|
|
/* multivariate MCV list - essentially an array of MCV items */
|
|
typedef struct MCVList
|
|
{
|
|
uint32 magic; /* magic constant marker */
|
|
uint32 type; /* type of MCV list (BASIC) */
|
|
uint32 nitems; /* number of MCV items in the array */
|
|
AttrNumber ndimensions; /* number of dimensions */
|
|
Oid types[STATS_MAX_DIMENSIONS]; /* OIDs of data types */
|
|
MCVItem items[FLEXIBLE_ARRAY_MEMBER]; /* array of MCV items */
|
|
} MCVList;
|
|
|
|
extern MVNDistinct *statext_ndistinct_load(Oid mvoid);
|
|
extern MVDependencies *statext_dependencies_load(Oid mvoid);
|
|
extern MCVList *statext_mcv_load(Oid mvoid);
|
|
|
|
extern void BuildRelationExtStatistics(Relation onerel, double totalrows,
|
|
int numrows, HeapTuple *rows,
|
|
int natts, VacAttrStats **vacattrstats);
|
|
extern int ComputeExtStatisticsRows(Relation onerel,
|
|
int natts, VacAttrStats **stats);
|
|
extern bool statext_is_kind_built(HeapTuple htup, char kind);
|
|
extern Selectivity dependencies_clauselist_selectivity(PlannerInfo *root,
|
|
List *clauses,
|
|
int varRelid,
|
|
JoinType jointype,
|
|
SpecialJoinInfo *sjinfo,
|
|
RelOptInfo *rel,
|
|
Bitmapset **estimatedclauses);
|
|
extern Selectivity statext_clauselist_selectivity(PlannerInfo *root,
|
|
List *clauses,
|
|
int varRelid,
|
|
JoinType jointype,
|
|
SpecialJoinInfo *sjinfo,
|
|
RelOptInfo *rel,
|
|
Bitmapset **estimatedclauses);
|
|
extern bool has_stats_of_kind(List *stats, char requiredkind);
|
|
extern StatisticExtInfo *choose_best_statistics(List *stats, char requiredkind,
|
|
Bitmapset **clause_attnums,
|
|
int nclauses);
|
|
|
|
#endif /* STATISTICS_H */
|