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db_include/utils/selfuncs.h
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241
db_include/utils/selfuncs.h
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/*-------------------------------------------------------------------------
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*
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* selfuncs.h
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* Selectivity functions for standard operators, and assorted
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* infrastructure for selectivity and cost estimation.
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*
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*
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* Portions Copyright (c) 1996-2021, 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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* src/include/utils/selfuncs.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SELFUNCS_H
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#define SELFUNCS_H
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#include "access/htup.h"
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#include "fmgr.h"
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#include "nodes/pathnodes.h"
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/*
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* Note: the default selectivity estimates are not chosen entirely at random.
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* We want them to be small enough to ensure that indexscans will be used if
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* available, for typical table densities of ~100 tuples/page. Thus, for
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* example, 0.01 is not quite small enough, since that makes it appear that
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* nearly all pages will be hit anyway. Also, since we sometimes estimate
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* eqsel as 1/num_distinct, we probably want DEFAULT_NUM_DISTINCT to equal
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* 1/DEFAULT_EQ_SEL.
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*/
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/* default selectivity estimate for equalities such as "A = b" */
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#define DEFAULT_EQ_SEL 0.005
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/* default selectivity estimate for inequalities such as "A < b" */
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#define DEFAULT_INEQ_SEL 0.3333333333333333
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/* default selectivity estimate for range inequalities "A > b AND A < c" */
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#define DEFAULT_RANGE_INEQ_SEL 0.005
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/* default selectivity estimate for multirange inequalities "A > b AND A < c" */
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#define DEFAULT_MULTIRANGE_INEQ_SEL 0.005
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/* default selectivity estimate for pattern-match operators such as LIKE */
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#define DEFAULT_MATCH_SEL 0.005
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/* default selectivity estimate for other matching operators */
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#define DEFAULT_MATCHING_SEL 0.010
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/* default number of distinct values in a table */
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#define DEFAULT_NUM_DISTINCT 200
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/* default selectivity estimate for boolean and null test nodes */
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#define DEFAULT_UNK_SEL 0.005
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#define DEFAULT_NOT_UNK_SEL (1.0 - DEFAULT_UNK_SEL)
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/*
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* Clamp a computed probability estimate (which may suffer from roundoff or
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* estimation errors) to valid range. Argument must be a float variable.
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*/
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#define CLAMP_PROBABILITY(p) \
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do { \
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if (p < 0.0) \
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p = 0.0; \
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else if (p > 1.0) \
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p = 1.0; \
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} while (0)
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/*
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* A set of flags which some selectivity estimation functions can pass back to
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* callers to provide further details about some assumptions which were made
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* during the estimation.
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*/
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#define SELFLAG_USED_DEFAULT (1 << 0) /* Estimation fell back on one
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* of the DEFAULTs as defined
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* above. */
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typedef struct EstimationInfo
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{
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uint32 flags; /* Flags, as defined above to mark special
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* properties of the estimation. */
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} EstimationInfo;
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/* Return data from examine_variable and friends */
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typedef struct VariableStatData
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{
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Node *var; /* the Var or expression tree */
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RelOptInfo *rel; /* Relation, or NULL if not identifiable */
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HeapTuple statsTuple; /* pg_statistic tuple, or NULL if none */
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/* NB: if statsTuple!=NULL, it must be freed when caller is done */
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void (*freefunc) (HeapTuple tuple); /* how to free statsTuple */
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Oid vartype; /* exposed type of expression */
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Oid atttype; /* actual type (after stripping relabel) */
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int32 atttypmod; /* actual typmod (after stripping relabel) */
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bool isunique; /* matches unique index or DISTINCT clause */
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bool acl_ok; /* result of ACL check on table or column */
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} VariableStatData;
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#define ReleaseVariableStats(vardata) \
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do { \
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if (HeapTupleIsValid((vardata).statsTuple)) \
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(vardata).freefunc((vardata).statsTuple); \
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} while(0)
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/*
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* genericcostestimate is a general-purpose estimator that can be used for
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* most index types. In some cases we use genericcostestimate as the base
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* code and then incorporate additional index-type-specific knowledge in
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* the type-specific calling function. To avoid code duplication, we make
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* genericcostestimate return a number of intermediate values as well as
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* its preliminary estimates of the output cost values. The GenericCosts
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* struct includes all these values.
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*
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* Callers should initialize all fields of GenericCosts to zero. In addition,
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* they can set numIndexTuples to some positive value if they have a better
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* than default way of estimating the number of leaf index tuples visited.
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*/
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typedef struct
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{
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/* These are the values the cost estimator must return to the planner */
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Cost indexStartupCost; /* index-related startup cost */
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Cost indexTotalCost; /* total index-related scan cost */
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Selectivity indexSelectivity; /* selectivity of index */
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double indexCorrelation; /* order correlation of index */
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/* Intermediate values we obtain along the way */
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double numIndexPages; /* number of leaf pages visited */
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double numIndexTuples; /* number of leaf tuples visited */
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double spc_random_page_cost; /* relevant random_page_cost value */
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double num_sa_scans; /* # indexscans from ScalarArrayOpExprs */
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} GenericCosts;
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/* Hooks for plugins to get control when we ask for stats */
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typedef bool (*get_relation_stats_hook_type) (PlannerInfo *root,
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RangeTblEntry *rte,
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AttrNumber attnum,
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VariableStatData *vardata);
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extern PGDLLIMPORT get_relation_stats_hook_type get_relation_stats_hook;
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typedef bool (*get_index_stats_hook_type) (PlannerInfo *root,
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Oid indexOid,
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AttrNumber indexattnum,
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VariableStatData *vardata);
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extern PGDLLIMPORT get_index_stats_hook_type get_index_stats_hook;
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/* Functions in selfuncs.c */
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extern void examine_variable(PlannerInfo *root, Node *node, int varRelid,
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VariableStatData *vardata);
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extern bool statistic_proc_security_check(VariableStatData *vardata, Oid func_oid);
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extern bool get_restriction_variable(PlannerInfo *root, List *args,
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int varRelid,
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VariableStatData *vardata, Node **other,
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bool *varonleft);
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extern void get_join_variables(PlannerInfo *root, List *args,
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SpecialJoinInfo *sjinfo,
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VariableStatData *vardata1,
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VariableStatData *vardata2,
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bool *join_is_reversed);
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extern double get_variable_numdistinct(VariableStatData *vardata,
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bool *isdefault);
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extern double mcv_selectivity(VariableStatData *vardata,
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FmgrInfo *opproc, Oid collation,
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Datum constval, bool varonleft,
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double *sumcommonp);
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extern double histogram_selectivity(VariableStatData *vardata,
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FmgrInfo *opproc, Oid collation,
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Datum constval, bool varonleft,
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int min_hist_size, int n_skip,
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int *hist_size);
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extern double generic_restriction_selectivity(PlannerInfo *root,
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Oid oproid, Oid collation,
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List *args, int varRelid,
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double default_selectivity);
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extern double ineq_histogram_selectivity(PlannerInfo *root,
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VariableStatData *vardata,
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Oid opoid, FmgrInfo *opproc,
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bool isgt, bool iseq,
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Oid collation,
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Datum constval, Oid consttype);
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extern double var_eq_const(VariableStatData *vardata,
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Oid oproid, Oid collation,
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Datum constval, bool constisnull,
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bool varonleft, bool negate);
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extern double var_eq_non_const(VariableStatData *vardata,
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Oid oproid, Oid collation,
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Node *other,
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bool varonleft, bool negate);
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extern Selectivity boolvarsel(PlannerInfo *root, Node *arg, int varRelid);
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extern Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype,
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Node *arg, int varRelid,
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JoinType jointype, SpecialJoinInfo *sjinfo);
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extern Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype,
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Node *arg, int varRelid,
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JoinType jointype, SpecialJoinInfo *sjinfo);
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extern Selectivity scalararraysel(PlannerInfo *root,
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ScalarArrayOpExpr *clause,
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bool is_join_clause,
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int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
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extern int estimate_array_length(Node *arrayexpr);
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extern Selectivity rowcomparesel(PlannerInfo *root,
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RowCompareExpr *clause,
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int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
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extern void mergejoinscansel(PlannerInfo *root, Node *clause,
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Oid opfamily, int strategy, bool nulls_first,
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Selectivity *leftstart, Selectivity *leftend,
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Selectivity *rightstart, Selectivity *rightend);
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extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
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double input_rows, List **pgset,
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EstimationInfo *estinfo);
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extern void estimate_hash_bucket_stats(PlannerInfo *root,
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Node *hashkey, double nbuckets,
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Selectivity *mcv_freq,
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Selectivity *bucketsize_frac);
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extern double estimate_hashagg_tablesize(PlannerInfo *root, Path *path,
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const AggClauseCosts *agg_costs,
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double dNumGroups);
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extern List *get_quals_from_indexclauses(List *indexclauses);
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extern Cost index_other_operands_eval_cost(PlannerInfo *root,
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List *indexquals);
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extern List *add_predicate_to_index_quals(IndexOptInfo *index,
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List *indexQuals);
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extern void genericcostestimate(PlannerInfo *root, IndexPath *path,
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double loop_count,
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GenericCosts *costs);
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/* Functions in array_selfuncs.c */
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extern Selectivity scalararraysel_containment(PlannerInfo *root,
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Node *leftop, Node *rightop,
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Oid elemtype, bool isEquality, bool useOr,
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int varRelid);
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#endif /* SELFUNCS_H */
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