text: /*-------------------------------------------------------------------------
   *
   * paths.h
   *	  prototypes for various files in optimizer/path
   *
   *
   * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * src/include/optimizer/paths.h
   *
   *-------------------------------------------------------------------------
   */
  #ifndef PATHS_H
  #define PATHS_H
  
  #include "nodes/relation.h"
  
  
  /*
   * allpaths.c
   */
  extern bool enable_geqo;
  extern int	geqo_threshold;
  extern int	min_parallel_relation_size;
  
  /* Hook for plugins to get control in set_rel_pathlist() */
  typedef void (*set_rel_pathlist_hook_type) (PlannerInfo *root,
  														RelOptInfo *rel,
  														Index rti,
  														RangeTblEntry *rte);
  extern PGDLLIMPORT set_rel_pathlist_hook_type set_rel_pathlist_hook;
  
  /* Hook for plugins to get control in add_paths_to_joinrel() */
  typedef void (*set_join_pathlist_hook_type) (PlannerInfo *root,
  														 RelOptInfo *joinrel,
  														 RelOptInfo *outerrel,
  														 RelOptInfo *innerrel,
  														 JoinType jointype,
  												   JoinPathExtraData *extra);
  extern PGDLLIMPORT set_join_pathlist_hook_type set_join_pathlist_hook;
  
  /* Hook for plugins to replace standard_join_search() */
  typedef RelOptInfo *(*join_search_hook_type) (PlannerInfo *root,
  														  int levels_needed,
  														  List *initial_rels);
  extern PGDLLIMPORT join_search_hook_type join_search_hook;
  
  
  extern RelOptInfo *make_one_rel(PlannerInfo *root, List *joinlist);
  extern void set_dummy_rel_pathlist(RelOptInfo *rel);
  extern RelOptInfo *standard_join_search(PlannerInfo *root, int levels_needed,
  					 List *initial_rels);
  
  extern void generate_gather_paths(PlannerInfo *root, RelOptInfo *rel);
  
  #ifdef OPTIMIZER_DEBUG
  extern void debug_print_rel(PlannerInfo *root, RelOptInfo *rel);
  #endif
  
  /*
   * indxpath.c
   *	  routines to generate index paths
   */
  extern void create_index_paths(PlannerInfo *root, RelOptInfo *rel);
  extern bool relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
  							  List *restrictlist,
  							  List *exprlist, List *oprlist);
  extern bool match_index_to_operand(Node *operand, int indexcol,
  					   IndexOptInfo *index);
  extern void expand_indexqual_conditions(IndexOptInfo *index,
  							List *indexclauses, List *indexclausecols,
  							List **indexquals_p, List **indexqualcols_p);
  extern void check_index_predicates(PlannerInfo *root, RelOptInfo *rel);
  extern Expr *adjust_rowcompare_for_index(RowCompareExpr *clause,
  							IndexOptInfo *index,
  							int indexcol,
  							List **indexcolnos,
  							bool *var_on_left_p);
  
  /*
   * tidpath.h
   *	  routines to generate tid paths
   */
  extern void create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel);
  
  /*
   * joinpath.c
   *	   routines to create join paths
   */
  extern void add_paths_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
  					 RelOptInfo *outerrel, RelOptInfo *innerrel,
  					 JoinType jointype, SpecialJoinInfo *sjinfo,
  					 List *restrictlist);
  
  /*
   * joinrels.c
   *	  routines to determine which relations to join
   */
  extern void join_search_one_level(PlannerInfo *root, int level);
  extern RelOptInfo *make_join_rel(PlannerInfo *root,
  			  RelOptInfo *rel1, RelOptInfo *rel2);
  extern bool have_join_order_restriction(PlannerInfo *root,
  							RelOptInfo *rel1, RelOptInfo *rel2);
  extern bool have_dangerous_phv(PlannerInfo *root,
  				   Relids outer_relids, Relids inner_params);
  
  /*
   * equivclass.c
   *	  routines for managing EquivalenceClasses
   */
  typedef bool (*ec_matches_callback_type) (PlannerInfo *root,
  													  RelOptInfo *rel,
  													  EquivalenceClass *ec,
  													  EquivalenceMember *em,
  													  void *arg);
  
  extern bool process_equivalence(PlannerInfo *root, RestrictInfo *restrictinfo,
  					bool below_outer_join);
  extern Expr *canonicalize_ec_expression(Expr *expr,
  						   Oid req_type, Oid req_collation);
  extern void reconsider_outer_join_clauses(PlannerInfo *root);
  extern EquivalenceClass *get_eclass_for_sort_expr(PlannerInfo *root,
  						 Expr *expr,
  						 Relids nullable_relids,
  						 List *opfamilies,
  						 Oid opcintype,
  						 Oid collation,
  						 Index sortref,
  						 Relids rel,
  						 bool create_it);
  extern void generate_base_implied_equalities(PlannerInfo *root);
  extern List *generate_join_implied_equalities(PlannerInfo *root,
  								 Relids join_relids,
  								 Relids outer_relids,
  								 RelOptInfo *inner_rel);
  extern List *generate_join_implied_equalities_for_ecs(PlannerInfo *root,
  										 List *eclasses,
  										 Relids join_relids,
  										 Relids outer_relids,
  										 RelOptInfo *inner_rel);
  extern bool exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2);
  extern EquivalenceClass *match_eclasses_to_foreign_key_col(PlannerInfo *root,
  								  ForeignKeyOptInfo *fkinfo,
  								  int colno);
  extern void add_child_rel_equivalences(PlannerInfo *root,
  						   AppendRelInfo *appinfo,
  						   RelOptInfo *parent_rel,
  						   RelOptInfo *child_rel);
  extern List *generate_implied_equalities_for_column(PlannerInfo *root,
  									   RelOptInfo *rel,
  									   ec_matches_callback_type callback,
  									   void *callback_arg,
  									   Relids prohibited_rels);
  extern bool have_relevant_eclass_joinclause(PlannerInfo *root,
  								RelOptInfo *rel1, RelOptInfo *rel2);
  extern bool has_relevant_eclass_joinclause(PlannerInfo *root,
  							   RelOptInfo *rel1);
  extern bool eclass_useful_for_merging(PlannerInfo *root,
  						  EquivalenceClass *eclass,
  						  RelOptInfo *rel);
  extern bool is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist);
  
  /*
   * pathkeys.c
   *	  utilities for matching and building path keys
   */
  typedef enum
  {
  	PATHKEYS_EQUAL,				/* pathkeys are identical */
  	PATHKEYS_BETTER1,			/* pathkey 1 is a superset of pathkey 2 */
  	PATHKEYS_BETTER2,			/* vice versa */
  	PATHKEYS_DIFFERENT			/* neither pathkey includes the other */
  } PathKeysComparison;
  
  extern PathKeysComparison compare_pathkeys(List *keys1, List *keys2);
  extern bool pathkeys_contained_in(List *keys1, List *keys2);
  extern Path *get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
  							   Relids required_outer,
  							   CostSelector cost_criterion);
  extern Path *get_cheapest_fractional_path_for_pathkeys(List *paths,
  										  List *pathkeys,
  										  Relids required_outer,
  										  double fraction);
  extern List *build_index_pathkeys(PlannerInfo *root, IndexOptInfo *index,
  					 ScanDirection scandir);
  extern List *build_expression_pathkey(PlannerInfo *root, Expr *expr,
  						 Relids nullable_relids, Oid opno,
  						 Relids rel, bool create_it);
  extern List *convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
  						  List *subquery_pathkeys,
  						  List *subquery_tlist);
  extern List *build_join_pathkeys(PlannerInfo *root,
  					RelOptInfo *joinrel,
  					JoinType jointype,
  					List *outer_pathkeys);
  extern List *make_pathkeys_for_sortclauses(PlannerInfo *root,
  							  List *sortclauses,
  							  List *tlist);
  extern void initialize_mergeclause_eclasses(PlannerInfo *root,
  								RestrictInfo *restrictinfo);
  extern void update_mergeclause_eclasses(PlannerInfo *root,
  							RestrictInfo *restrictinfo);
  extern List *find_mergeclauses_for_pathkeys(PlannerInfo *root,
  							   List *pathkeys,
  							   bool outer_keys,
  							   List *restrictinfos);
  extern List *select_outer_pathkeys_for_merge(PlannerInfo *root,
  								List *mergeclauses,
  								RelOptInfo *joinrel);
  extern List *make_inner_pathkeys_for_merge(PlannerInfo *root,
  							  List *mergeclauses,
  							  List *outer_pathkeys);
  extern List *truncate_useless_pathkeys(PlannerInfo *root,
  						  RelOptInfo *rel,
  						  List *pathkeys);
  extern bool has_useful_pathkeys(PlannerInfo *root, RelOptInfo *rel);
  extern PathKey *make_canonical_pathkey(PlannerInfo *root,
  					   EquivalenceClass *eclass, Oid opfamily,
  					   int strategy, bool nulls_first);
  
  #endif   /* PATHS_H */
  