src/libpq/include/utils/selfuncs.h

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/*-------------------------------------------------------------------------
 *
 * selfuncs.h
 *        Selectivity functions and index cost estimation functions for
 *        standard operators and index access methods.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.24 2005/10/15 02:49:46 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef SELFUNCS_H
#define SELFUNCS_H

#include "fmgr.h"
#include "nodes/relation.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 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)


typedef enum
{
        Pattern_Type_Like, Pattern_Type_Like_IC,
        Pattern_Type_Regex, Pattern_Type_Regex_IC
} Pattern_Type;

typedef enum
{
        Pattern_Prefix_None, Pattern_Prefix_Partial, Pattern_Prefix_Exact
} Pattern_Prefix_Status;


/* selfuncs.c */

extern Pattern_Prefix_Status pattern_fixed_prefix(Const *patt,
                                         Pattern_Type ptype,
                                         Const **prefix,
                                         Const **rest);
extern Const *make_greater_string(const Const *str_const);

extern Datum eqsel(PG_FUNCTION_ARGS);
extern Datum neqsel(PG_FUNCTION_ARGS);
extern Datum scalarltsel(PG_FUNCTION_ARGS);
extern Datum scalargtsel(PG_FUNCTION_ARGS);
extern Datum regexeqsel(PG_FUNCTION_ARGS);
extern Datum icregexeqsel(PG_FUNCTION_ARGS);
extern Datum likesel(PG_FUNCTION_ARGS);
extern Datum iclikesel(PG_FUNCTION_ARGS);
extern Datum regexnesel(PG_FUNCTION_ARGS);
extern Datum icregexnesel(PG_FUNCTION_ARGS);
extern Datum nlikesel(PG_FUNCTION_ARGS);
extern Datum icnlikesel(PG_FUNCTION_ARGS);

extern Datum eqjoinsel(PG_FUNCTION_ARGS);
extern Datum neqjoinsel(PG_FUNCTION_ARGS);
extern Datum scalarltjoinsel(PG_FUNCTION_ARGS);
extern Datum scalargtjoinsel(PG_FUNCTION_ARGS);
extern Datum regexeqjoinsel(PG_FUNCTION_ARGS);
extern Datum icregexeqjoinsel(PG_FUNCTION_ARGS);
extern Datum likejoinsel(PG_FUNCTION_ARGS);
extern Datum iclikejoinsel(PG_FUNCTION_ARGS);
extern Datum regexnejoinsel(PG_FUNCTION_ARGS);
extern Datum icregexnejoinsel(PG_FUNCTION_ARGS);
extern Datum nlikejoinsel(PG_FUNCTION_ARGS);
extern Datum icnlikejoinsel(PG_FUNCTION_ARGS);

extern Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype,
                        Node *arg, int varRelid, JoinType jointype);
extern Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype,
                        Node *arg, int varRelid);

extern void mergejoinscansel(PlannerInfo *root, Node *clause,
                                 Selectivity *leftscan,
                                 Selectivity *rightscan);

extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
                                        double input_rows);

extern Selectivity estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey,
                                                 double nbuckets);

extern Datum btcostestimate(PG_FUNCTION_ARGS);
extern Datum rtcostestimate(PG_FUNCTION_ARGS);
extern Datum hashcostestimate(PG_FUNCTION_ARGS);
extern Datum gistcostestimate(PG_FUNCTION_ARGS);

#endif   /* SELFUNCS_H */