text: /*-------------------------------------------------------------------------
   *
   * selfuncs.h
   *	  Selectivity functions and index cost estimation functions for
   *	  standard operators and index access methods.
   *
   *
   * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.49 2009/06/11 14:49:13 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
  #ifndef SELFUNCS_H
  #define SELFUNCS_H
  
  #include "fmgr.h"
  #include "access/htup.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)
  
  
  /* 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;		/* type to pass to get_attstatsslot */
  	int32		atttypmod;		/* typmod to pass to get_attstatsslot */
  	bool		isunique;		/* true if matched to a unique index */
  } VariableStatData;
  
  #define ReleaseVariableStats(vardata)  \
  	do { \
  		if (HeapTupleIsValid((vardata).statsTuple)) \
  			(* (vardata).freefunc) ((vardata).statsTuple); \
  	} 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 */
  
  /* 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;
  
  extern void examine_variable(PlannerInfo *root, Node *node, int varRelid,
  				 VariableStatData *vardata);
  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);
  extern double mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
  				Datum constval, bool varonleft,
  				double *sumcommonp);
  extern double histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
  					  Datum constval, bool varonleft,
  					  int min_hist_size, int n_skip,
  					  int *hist_size);
  
  extern Pattern_Prefix_Status pattern_fixed_prefix(Const *patt,
  					 Pattern_Type ptype,
  					 Const **prefix,
  					 Selectivity *rest_selec);
  extern Const *make_greater_string(const Const *str_const, FmgrInfo *ltproc);
  
  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, 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);
  
  extern Selectivity estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey,
  						 double nbuckets);
  
  extern Datum btcostestimate(PG_FUNCTION_ARGS);
  extern Datum hashcostestimate(PG_FUNCTION_ARGS);
  extern Datum gistcostestimate(PG_FUNCTION_ARGS);
  extern Datum gincostestimate(PG_FUNCTION_ARGS);
  
  #endif   /* SELFUNCS_H */
  