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/*-------------------------------------------------------------------------
*
* selfuncs.h
* Selectivity functions for standard operators, and assorted
* infrastructure for selectivity and cost estimation.
*
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/selfuncs.h
*
*-------------------------------------------------------------------------
*/
#ifndef SELFUNCS_H
#define SELFUNCS_H
#include "access/htup.h"
#include "fmgr.h"
#include "nodes/pathnodes.h"
/*
* Note: the default selectivity estimates are not chosen entirely at random.
* We want them to be small enough to ensure that indexscans will be used if
* available, for typical table densities of ~100 tuples/page. Thus, for
* example, 0.01 is not quite small enough, since that makes it appear that
* nearly all pages will be hit anyway. Also, since we sometimes estimate
* eqsel as 1/num_distinct, we probably want DEFAULT_NUM_DISTINCT to equal
* 1/DEFAULT_EQ_SEL.
*/
/* default selectivity estimate for equalities such as "A = b" */
#define DEFAULT_EQ_SEL 0.005
/* default selectivity estimate for inequalities such as "A < b" */
#define DEFAULT_INEQ_SEL 0.3333333333333333
/* default selectivity estimate for range inequalities "A > b AND A < c" */
#define DEFAULT_RANGE_INEQ_SEL 0.005
/* default selectivity estimate for pattern-match operators such as LIKE */
#define DEFAULT_MATCH_SEL 0.005
/* default selectivity estimate for other matching operators */
#define DEFAULT_MATCHING_SEL 0.010
/* default number of distinct values in a table */
#define DEFAULT_NUM_DISTINCT 200
/* default selectivity estimate for boolean and null test nodes */
#define DEFAULT_UNK_SEL 0.005
#define DEFAULT_NOT_UNK_SEL (1.0 - DEFAULT_UNK_SEL)
/*
* Clamp a computed probability estimate (which may suffer from roundoff or
* estimation errors) to valid range. Argument must be a float variable.
*/
#define CLAMP_PROBABILITY(p) \
do { \
if (p < 0.0) \
p = 0.0; \
else if (p > 1.0) \
p = 1.0; \
} while (0)
/* Return data from examine_variable and friends */
typedef struct VariableStatData
{
Node *var; /* the Var or expression tree */
RelOptInfo *rel; /* Relation, or NULL if not identifiable */
HeapTuple statsTuple; /* pg_statistic tuple, or NULL if none */
/* NB: if statsTuple!=NULL, it must be freed when caller is done */
void (*freefunc) (HeapTuple tuple); /* how to free statsTuple */
Oid vartype; /* exposed type of expression */
Oid atttype; /* actual type (after stripping relabel) */
int32 atttypmod; /* actual typmod (after stripping relabel) */
bool isunique; /* matches unique index or DISTINCT clause */
bool acl_ok; /* result of ACL check on table or column */
} VariableStatData;
#define ReleaseVariableStats(vardata) \
do { \
if (HeapTupleIsValid((vardata).statsTuple)) \
(vardata).freefunc((vardata).statsTuple); \
} while(0)
/*
* genericcostestimate is a general-purpose estimator that can be used for
* most index types. In some cases we use genericcostestimate as the base
* code and then incorporate additional index-type-specific knowledge in
* the type-specific calling function. To avoid code duplication, we make
* genericcostestimate return a number of intermediate values as well as
* its preliminary estimates of the output cost values. The GenericCosts
* struct includes all these values.
*
* Callers should initialize all fields of GenericCosts to zero. In addition,
* they can set numIndexTuples to some positive value if they have a better
* than default way of estimating the number of leaf index tuples visited.
*/
typedef struct
{
/* These are the values the cost estimator must return to the planner */
Cost indexStartupCost; /* index-related startup cost */
Cost indexTotalCost; /* total index-related scan cost */
Selectivity indexSelectivity; /* selectivity of index */
double indexCorrelation; /* order correlation of index */
/* Intermediate values we obtain along the way */
double numIndexPages; /* number of leaf pages visited */
double numIndexTuples; /* number of leaf tuples visited */
double spc_random_page_cost; /* relevant random_page_cost value */
double num_sa_scans; /* # indexscans from ScalarArrayOpExprs */
} GenericCosts;
/* Hooks for plugins to get control when we ask for stats */
typedef bool (*get_relation_stats_hook_type) (PlannerInfo *root,
RangeTblEntry *rte,
AttrNumber attnum,
VariableStatData *vardata);
extern PGDLLIMPORT get_relation_stats_hook_type get_relation_stats_hook;
typedef bool (*get_index_stats_hook_type) (PlannerInfo *root,
Oid indexOid,
AttrNumber indexattnum,
VariableStatData *vardata);
extern PGDLLIMPORT get_index_stats_hook_type get_index_stats_hook;
/* Functions in selfuncs.c */
extern void examine_variable(PlannerInfo *root, Node *node, int varRelid,
VariableStatData *vardata);
extern bool statistic_proc_security_check(VariableStatData *vardata, Oid func_oid);
extern bool get_restriction_variable(PlannerInfo *root, List *args,
int varRelid,
VariableStatData *vardata, Node **other,
bool *varonleft);
extern void get_join_variables(PlannerInfo *root, List *args,
SpecialJoinInfo *sjinfo,
VariableStatData *vardata1,
VariableStatData *vardata2,
bool *join_is_reversed);
extern double get_variable_numdistinct(VariableStatData *vardata,
bool *isdefault);
extern double mcv_selectivity(VariableStatData *vardata,
FmgrInfo *opproc, Oid collation,
Datum constval, bool varonleft,
double *sumcommonp);
extern double histogram_selectivity(VariableStatData *vardata,
FmgrInfo *opproc, Oid collation,
Datum constval, bool varonleft,
int min_hist_size, int n_skip,
int *hist_size);
extern double generic_restriction_selectivity(PlannerInfo *root,
Oid oproid, Oid collation,
List *args, int varRelid,
double default_selectivity);
extern double ineq_histogram_selectivity(PlannerInfo *root,
VariableStatData *vardata,
Oid opoid, FmgrInfo *opproc,
bool isgt, bool iseq,
Oid collation,
Datum constval, Oid consttype);
extern double var_eq_const(VariableStatData *vardata,
Oid oproid, Oid collation,
Datum constval, bool constisnull,
bool varonleft, bool negate);
extern double var_eq_non_const(VariableStatData *vardata,
Oid oproid, Oid collation,
Node *other,
bool varonleft, bool negate);
extern Selectivity boolvarsel(PlannerInfo *root, Node *arg, int varRelid);
extern Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype,
Node *arg, int varRelid,
JoinType jointype, SpecialJoinInfo *sjinfo);
extern Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype,
Node *arg, int varRelid,
JoinType jointype, SpecialJoinInfo *sjinfo);
extern Selectivity scalararraysel(PlannerInfo *root,
ScalarArrayOpExpr *clause,
bool is_join_clause,
int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
extern int estimate_array_length(Node *arrayexpr);
extern Selectivity rowcomparesel(PlannerInfo *root,
RowCompareExpr *clause,
int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
extern void mergejoinscansel(PlannerInfo *root, Node *clause,
Oid opfamily, int strategy, bool nulls_first,
Selectivity *leftstart, Selectivity *leftend,
Selectivity *rightstart, Selectivity *rightend);
extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
double input_rows, List **pgset);
extern void estimate_hash_bucket_stats(PlannerInfo *root,
Node *hashkey, double nbuckets,
Selectivity *mcv_freq,
Selectivity *bucketsize_frac);
extern double estimate_hashagg_tablesize(Path *path,
const AggClauseCosts *agg_costs,
double dNumGroups);
extern List *get_quals_from_indexclauses(List *indexclauses);
extern Cost index_other_operands_eval_cost(PlannerInfo *root,
List *indexquals);
extern List *add_predicate_to_index_quals(IndexOptInfo *index,
List *indexQuals);
extern void genericcostestimate(PlannerInfo *root, IndexPath *path,
double loop_count,
GenericCosts *costs);
/* Functions in array_selfuncs.c */
extern Selectivity scalararraysel_containment(PlannerInfo *root,
Node *leftop, Node *rightop,
Oid elemtype, bool isEquality, bool useOr,
int varRelid);
#endif /* SELFUNCS_H */
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