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There are two implementation techniques for semijoins: one uses the JOIN_SEMI jointype, where the executor emits at most one matching row per left-hand side (LHS) row; the other unique-ifies the right-hand side (RHS) and then performs a plain inner join. The latter technique currently has some drawbacks related to the unique-ification step. * Only the cheapest-total path of the RHS is considered during unique-ification. This may cause us to miss some optimization opportunities; for example, a path with a better sort order might be overlooked simply because it is not the cheapest in total cost. Such a path could help avoid a sort at a higher level, potentially resulting in a cheaper overall plan. * We currently rely on heuristics to choose between hash-based and sort-based unique-ification. A better approach would be to generate paths for both methods and allow add_path() to decide which one is preferable, consistent with how path selection is handled elsewhere in the planner. * In the sort-based implementation, we currently pay no attention to the pathkeys of the input subpath or the resulting output. This can result in redundant sort nodes being added to the final plan. This patch improves semijoin planning by creating a new RelOptInfo for the RHS rel to represent its unique-ified version. It then generates multiple paths that represent elimination of distinct rows from the RHS, considering both a hash-based implementation using the cheapest total path of the original RHS rel, and sort-based implementations that either exploit presorted input paths or explicitly sort the cheapest total path. All resulting paths compete in add_path(), and those deemed worthy of consideration are added to the new RelOptInfo. Finally, the unique-ified rel is joined with the other side of the semijoin using a plain inner join. As a side effect, most of the code related to the JOIN_UNIQUE_OUTER and JOIN_UNIQUE_INNER jointypes -- used to indicate that the LHS or RHS path should be made unique -- has been removed. Besides, the T_Unique path now has the same meaning for both semijoins and upper DISTINCT clauses: it represents adjacent-duplicate removal on presorted input. This patch unifies their handling by sharing the same data structures and functions. This patch also removes the UNIQUE_PATH_NOOP related code along the way, as it is dead code -- if the RHS rel is provably unique, the semijoin should have already been simplified to a plain inner join by analyzejoins.c. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Alexandra Wang <alexandra.wang.oss@gmail.com> Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com> Discussion: https://postgr.es/m/CAMbWs4-EBnaRvEs7frTLbsXiweSTUXifsteF-d3rvv01FKO86w@mail.gmail.com
354 lines
14 KiB
C
354 lines
14 KiB
C
/*-------------------------------------------------------------------------
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*
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* pathnode.h
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* prototypes for pathnode.c, relnode.c.
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*
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*
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* Portions Copyright (c) 1996-2025, 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/optimizer/pathnode.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PATHNODE_H
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#define PATHNODE_H
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#include "nodes/bitmapset.h"
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#include "nodes/pathnodes.h"
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/*
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* prototypes for pathnode.c
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*/
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extern int compare_path_costs(Path *path1, Path *path2,
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CostSelector criterion);
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extern int compare_fractional_path_costs(Path *path1, Path *path2,
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double fraction);
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extern void set_cheapest(RelOptInfo *parent_rel);
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extern void add_path(RelOptInfo *parent_rel, Path *new_path);
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extern bool add_path_precheck(RelOptInfo *parent_rel, int disabled_nodes,
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Cost startup_cost, Cost total_cost,
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List *pathkeys, Relids required_outer);
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extern void add_partial_path(RelOptInfo *parent_rel, Path *new_path);
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extern bool add_partial_path_precheck(RelOptInfo *parent_rel,
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int disabled_nodes,
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Cost total_cost, List *pathkeys);
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extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer, int parallel_workers);
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extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern IndexPath *create_index_path(PlannerInfo *root,
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IndexOptInfo *index,
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List *indexclauses,
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List *indexorderbys,
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List *indexorderbycols,
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List *pathkeys,
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ScanDirection indexscandir,
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bool indexonly,
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Relids required_outer,
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double loop_count,
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bool partial_path);
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extern BitmapHeapPath *create_bitmap_heap_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *bitmapqual,
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Relids required_outer,
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double loop_count,
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int parallel_degree);
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extern BitmapAndPath *create_bitmap_and_path(PlannerInfo *root,
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RelOptInfo *rel,
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List *bitmapquals);
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extern BitmapOrPath *create_bitmap_or_path(PlannerInfo *root,
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RelOptInfo *rel,
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List *bitmapquals);
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extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
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List *tidquals, Relids required_outer);
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extern TidRangePath *create_tidrangescan_path(PlannerInfo *root,
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RelOptInfo *rel,
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List *tidrangequals,
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Relids required_outer);
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extern AppendPath *create_append_path(PlannerInfo *root, RelOptInfo *rel,
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List *subpaths, List *partial_subpaths,
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List *pathkeys, Relids required_outer,
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int parallel_workers, bool parallel_aware,
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double rows);
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extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
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RelOptInfo *rel,
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List *subpaths,
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List *pathkeys,
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Relids required_outer);
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extern GroupResultPath *create_group_result_path(PlannerInfo *root,
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RelOptInfo *rel,
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PathTarget *target,
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List *havingqual);
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extern MaterialPath *create_material_path(RelOptInfo *rel, Path *subpath);
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extern MemoizePath *create_memoize_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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List *param_exprs,
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List *hash_operators,
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bool singlerow,
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bool binary_mode,
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Cardinality est_calls);
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extern GatherPath *create_gather_path(PlannerInfo *root,
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RelOptInfo *rel, Path *subpath, PathTarget *target,
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Relids required_outer, double *rows);
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extern GatherMergePath *create_gather_merge_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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PathTarget *target,
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List *pathkeys,
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Relids required_outer,
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double *rows);
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extern SubqueryScanPath *create_subqueryscan_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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bool trivial_pathtarget,
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List *pathkeys,
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Relids required_outer);
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extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
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List *pathkeys, Relids required_outer);
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extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern Path *create_tablefuncscan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel,
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List *pathkeys, Relids required_outer);
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extern Path *create_namedtuplestorescan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern Path *create_resultscan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
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PathTarget *target,
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double rows, int disabled_nodes,
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Cost startup_cost, Cost total_cost,
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List *pathkeys,
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Relids required_outer,
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Path *fdw_outerpath,
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List *fdw_restrictinfo,
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List *fdw_private);
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extern ForeignPath *create_foreign_join_path(PlannerInfo *root, RelOptInfo *rel,
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PathTarget *target,
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double rows, int disabled_nodes,
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Cost startup_cost, Cost total_cost,
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List *pathkeys,
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Relids required_outer,
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Path *fdw_outerpath,
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List *fdw_restrictinfo,
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List *fdw_private);
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extern ForeignPath *create_foreign_upper_path(PlannerInfo *root, RelOptInfo *rel,
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PathTarget *target,
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double rows, int disabled_nodes,
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Cost startup_cost, Cost total_cost,
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List *pathkeys,
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Path *fdw_outerpath,
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List *fdw_restrictinfo,
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List *fdw_private);
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extern Relids calc_nestloop_required_outer(Relids outerrelids,
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Relids outer_paramrels,
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Relids innerrelids,
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Relids inner_paramrels);
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extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);
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extern NestPath *create_nestloop_path(PlannerInfo *root,
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RelOptInfo *joinrel,
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JoinType jointype,
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JoinCostWorkspace *workspace,
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JoinPathExtraData *extra,
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Path *outer_path,
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Path *inner_path,
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List *restrict_clauses,
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List *pathkeys,
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Relids required_outer);
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extern MergePath *create_mergejoin_path(PlannerInfo *root,
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RelOptInfo *joinrel,
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JoinType jointype,
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JoinCostWorkspace *workspace,
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JoinPathExtraData *extra,
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Path *outer_path,
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Path *inner_path,
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List *restrict_clauses,
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List *pathkeys,
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Relids required_outer,
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List *mergeclauses,
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List *outersortkeys,
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List *innersortkeys,
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int outer_presorted_keys);
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extern HashPath *create_hashjoin_path(PlannerInfo *root,
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RelOptInfo *joinrel,
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JoinType jointype,
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JoinCostWorkspace *workspace,
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JoinPathExtraData *extra,
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Path *outer_path,
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Path *inner_path,
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bool parallel_hash,
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List *restrict_clauses,
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Relids required_outer,
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List *hashclauses);
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extern ProjectionPath *create_projection_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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PathTarget *target);
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extern Path *apply_projection_to_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *path,
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PathTarget *target);
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extern ProjectSetPath *create_set_projection_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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PathTarget *target);
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extern SortPath *create_sort_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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List *pathkeys,
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double limit_tuples);
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extern IncrementalSortPath *create_incremental_sort_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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List *pathkeys,
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int presorted_keys,
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double limit_tuples);
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extern GroupPath *create_group_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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List *groupClause,
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List *qual,
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double numGroups);
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extern UniquePath *create_unique_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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int numCols,
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double numGroups);
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extern AggPath *create_agg_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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PathTarget *target,
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AggStrategy aggstrategy,
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AggSplit aggsplit,
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List *groupClause,
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List *qual,
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const AggClauseCosts *aggcosts,
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double numGroups);
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extern GroupingSetsPath *create_groupingsets_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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List *having_qual,
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AggStrategy aggstrategy,
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List *rollups,
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const AggClauseCosts *agg_costs);
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extern MinMaxAggPath *create_minmaxagg_path(PlannerInfo *root,
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RelOptInfo *rel,
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PathTarget *target,
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List *mmaggregates,
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List *quals);
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extern WindowAggPath *create_windowagg_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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PathTarget *target,
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List *windowFuncs,
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List *runCondition,
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WindowClause *winclause,
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List *qual,
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bool topwindow);
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extern SetOpPath *create_setop_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *leftpath,
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Path *rightpath,
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SetOpCmd cmd,
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SetOpStrategy strategy,
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List *groupList,
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double numGroups,
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double outputRows);
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extern RecursiveUnionPath *create_recursiveunion_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *leftpath,
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Path *rightpath,
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PathTarget *target,
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List *distinctList,
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int wtParam,
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double numGroups);
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extern LockRowsPath *create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
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Path *subpath, List *rowMarks, int epqParam);
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extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *subpath,
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CmdType operation, bool canSetTag,
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Index nominalRelation, Index rootRelation,
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bool partColsUpdated,
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List *resultRelations,
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List *updateColnosLists,
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List *withCheckOptionLists, List *returningLists,
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List *rowMarks, OnConflictExpr *onconflict,
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List *mergeActionLists, List *mergeJoinConditions,
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int epqParam);
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extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
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Path *subpath,
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Node *limitOffset, Node *limitCount,
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LimitOption limitOption,
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int64 offset_est, int64 count_est);
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extern void adjust_limit_rows_costs(double *rows,
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Cost *startup_cost, Cost *total_cost,
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int64 offset_est, int64 count_est);
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extern Path *reparameterize_path(PlannerInfo *root, Path *path,
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Relids required_outer,
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double loop_count);
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extern Path *reparameterize_path_by_child(PlannerInfo *root, Path *path,
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RelOptInfo *child_rel);
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extern bool path_is_reparameterizable_by_child(Path *path,
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RelOptInfo *child_rel);
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/*
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* prototypes for relnode.c
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*/
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extern void setup_simple_rel_arrays(PlannerInfo *root);
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extern void expand_planner_arrays(PlannerInfo *root, int add_size);
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extern RelOptInfo *build_simple_rel(PlannerInfo *root, int relid,
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RelOptInfo *parent);
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extern RelOptInfo *find_base_rel(PlannerInfo *root, int relid);
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extern RelOptInfo *find_base_rel_noerr(PlannerInfo *root, int relid);
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extern RelOptInfo *find_base_rel_ignore_join(PlannerInfo *root, int relid);
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extern RelOptInfo *find_join_rel(PlannerInfo *root, Relids relids);
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extern RelOptInfo *build_join_rel(PlannerInfo *root,
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Relids joinrelids,
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RelOptInfo *outer_rel,
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RelOptInfo *inner_rel,
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SpecialJoinInfo *sjinfo,
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List *pushed_down_joins,
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List **restrictlist_ptr);
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extern Relids min_join_parameterization(PlannerInfo *root,
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Relids joinrelids,
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RelOptInfo *outer_rel,
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RelOptInfo *inner_rel);
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extern RelOptInfo *fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind,
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Relids relids);
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extern Relids find_childrel_parents(PlannerInfo *root, RelOptInfo *rel);
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extern ParamPathInfo *get_baserel_parampathinfo(PlannerInfo *root,
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RelOptInfo *baserel,
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Relids required_outer);
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extern ParamPathInfo *get_joinrel_parampathinfo(PlannerInfo *root,
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RelOptInfo *joinrel,
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Path *outer_path,
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Path *inner_path,
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SpecialJoinInfo *sjinfo,
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Relids required_outer,
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List **restrict_clauses);
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extern ParamPathInfo *get_appendrel_parampathinfo(RelOptInfo *appendrel,
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Relids required_outer);
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extern ParamPathInfo *find_param_path_info(RelOptInfo *rel,
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Relids required_outer);
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extern Bitmapset *get_param_path_clause_serials(Path *path);
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extern RelOptInfo *build_child_join_rel(PlannerInfo *root,
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RelOptInfo *outer_rel, RelOptInfo *inner_rel,
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RelOptInfo *parent_joinrel, List *restrictlist,
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SpecialJoinInfo *sjinfo,
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int nappinfos, AppendRelInfo **appinfos);
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#endif /* PATHNODE_H */
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