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The original implementation of TABLESAMPLE modeled the tablesample method API on index access methods, which wasn't a good choice because, without specialized DDL commands, there's no way to build an extension that can implement a TSM. (Raw inserts into system catalogs are not an acceptable thing to do, because we can't undo them during DROP EXTENSION, nor will pg_upgrade behave sanely.) Instead adopt an API more like procedural language handlers or foreign data wrappers, wherein the only SQL-level support object needed is a single handler function identified by having a special return type. This lets us get rid of the supporting catalog altogether, so that no custom DDL support is needed for the feature. Adjust the API so that it can support non-constant tablesample arguments (the original coding assumed we could evaluate the argument expressions at ExecInitSampleScan time, which is undesirable even if it weren't outright unsafe), and discourage sampling methods from looking at invisible tuples. Make sure that the BERNOULLI and SYSTEM methods are genuinely repeatable within and across queries, as required by the SQL standard, and deal more honestly with methods that can't support that requirement. Make a full code-review pass over the tablesample additions, and fix assorted bugs, omissions, infelicities, and cosmetic issues (such as failure to put the added code stanzas in a consistent ordering). Improve EXPLAIN's output of tablesample plans, too. Back-patch to 9.5 so that we don't have to support the original API in production.
195 lines
7.5 KiB
C
195 lines
7.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* cost.h
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* prototypes for costsize.c and clausesel.c.
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*
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*
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* Portions Copyright (c) 1996-2015, 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/cost.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef COST_H
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#define COST_H
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#include "nodes/plannodes.h"
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#include "nodes/relation.h"
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/* defaults for costsize.c's Cost parameters */
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/* NB: cost-estimation code should use the variables, not these constants! */
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/* If you change these, update backend/utils/misc/postgresql.sample.conf */
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#define DEFAULT_SEQ_PAGE_COST 1.0
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#define DEFAULT_RANDOM_PAGE_COST 4.0
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#define DEFAULT_CPU_TUPLE_COST 0.01
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#define DEFAULT_CPU_INDEX_TUPLE_COST 0.005
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#define DEFAULT_CPU_OPERATOR_COST 0.0025
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#define DEFAULT_EFFECTIVE_CACHE_SIZE 524288 /* measured in pages */
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typedef enum
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{
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CONSTRAINT_EXCLUSION_OFF, /* do not use c_e */
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CONSTRAINT_EXCLUSION_ON, /* apply c_e to all rels */
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CONSTRAINT_EXCLUSION_PARTITION /* apply c_e to otherrels only */
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} ConstraintExclusionType;
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/*
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* prototypes for costsize.c
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* routines to compute costs and sizes
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*/
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/* parameter variables and flags */
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extern PGDLLIMPORT double seq_page_cost;
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extern PGDLLIMPORT double random_page_cost;
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extern PGDLLIMPORT double cpu_tuple_cost;
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extern PGDLLIMPORT double cpu_index_tuple_cost;
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extern PGDLLIMPORT double cpu_operator_cost;
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extern PGDLLIMPORT int effective_cache_size;
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extern Cost disable_cost;
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extern bool enable_seqscan;
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extern bool enable_indexscan;
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extern bool enable_indexonlyscan;
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extern bool enable_bitmapscan;
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extern bool enable_tidscan;
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extern bool enable_sort;
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extern bool enable_hashagg;
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extern bool enable_nestloop;
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extern bool enable_material;
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extern bool enable_mergejoin;
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extern bool enable_hashjoin;
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extern int constraint_exclusion;
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extern double clamp_row_est(double nrows);
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extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
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double index_pages, PlannerInfo *root);
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extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
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ParamPathInfo *param_info);
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extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
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ParamPathInfo *param_info);
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extern void cost_index(IndexPath *path, PlannerInfo *root,
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double loop_count);
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extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
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ParamPathInfo *param_info,
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Path *bitmapqual, double loop_count);
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extern void cost_bitmap_and_node(BitmapAndPath *path, PlannerInfo *root);
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extern void cost_bitmap_or_node(BitmapOrPath *path, PlannerInfo *root);
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extern void cost_bitmap_tree_node(Path *path, Cost *cost, Selectivity *selec);
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extern void cost_tidscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, List *tidquals, ParamPathInfo *param_info);
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extern void cost_subqueryscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, ParamPathInfo *param_info);
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extern void cost_functionscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, ParamPathInfo *param_info);
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extern void cost_valuesscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, ParamPathInfo *param_info);
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extern void cost_ctescan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, ParamPathInfo *param_info);
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extern void cost_recursive_union(Plan *runion, Plan *nrterm, Plan *rterm);
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extern void cost_sort(Path *path, PlannerInfo *root,
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List *pathkeys, Cost input_cost, double tuples, int width,
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Cost comparison_cost, int sort_mem,
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double limit_tuples);
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extern void cost_merge_append(Path *path, PlannerInfo *root,
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List *pathkeys, int n_streams,
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Cost input_startup_cost, Cost input_total_cost,
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double tuples);
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extern void cost_material(Path *path,
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Cost input_startup_cost, Cost input_total_cost,
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double tuples, int width);
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extern void cost_agg(Path *path, PlannerInfo *root,
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AggStrategy aggstrategy, const AggClauseCosts *aggcosts,
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int numGroupCols, double numGroups,
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Cost input_startup_cost, Cost input_total_cost,
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double input_tuples);
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extern void cost_windowagg(Path *path, PlannerInfo *root,
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List *windowFuncs, int numPartCols, int numOrderCols,
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Cost input_startup_cost, Cost input_total_cost,
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double input_tuples);
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extern void cost_group(Path *path, PlannerInfo *root,
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int numGroupCols, double numGroups,
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Cost input_startup_cost, Cost input_total_cost,
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double input_tuples);
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extern void initial_cost_nestloop(PlannerInfo *root,
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JoinCostWorkspace *workspace,
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JoinType jointype,
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Path *outer_path, Path *inner_path,
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SpecialJoinInfo *sjinfo,
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SemiAntiJoinFactors *semifactors);
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extern void final_cost_nestloop(PlannerInfo *root, NestPath *path,
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JoinCostWorkspace *workspace,
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SpecialJoinInfo *sjinfo,
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SemiAntiJoinFactors *semifactors);
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extern void initial_cost_mergejoin(PlannerInfo *root,
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JoinCostWorkspace *workspace,
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JoinType jointype,
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List *mergeclauses,
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Path *outer_path, Path *inner_path,
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List *outersortkeys, List *innersortkeys,
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SpecialJoinInfo *sjinfo);
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extern void final_cost_mergejoin(PlannerInfo *root, MergePath *path,
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JoinCostWorkspace *workspace,
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SpecialJoinInfo *sjinfo);
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extern void initial_cost_hashjoin(PlannerInfo *root,
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JoinCostWorkspace *workspace,
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JoinType jointype,
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List *hashclauses,
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Path *outer_path, Path *inner_path,
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SpecialJoinInfo *sjinfo,
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SemiAntiJoinFactors *semifactors);
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extern void final_cost_hashjoin(PlannerInfo *root, HashPath *path,
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JoinCostWorkspace *workspace,
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SpecialJoinInfo *sjinfo,
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SemiAntiJoinFactors *semifactors);
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extern void cost_subplan(PlannerInfo *root, SubPlan *subplan, Plan *plan);
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extern void cost_qual_eval(QualCost *cost, List *quals, PlannerInfo *root);
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extern void cost_qual_eval_node(QualCost *cost, Node *qual, PlannerInfo *root);
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extern void compute_semi_anti_join_factors(PlannerInfo *root,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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JoinType jointype,
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SpecialJoinInfo *sjinfo,
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List *restrictlist,
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SemiAntiJoinFactors *semifactors);
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extern void set_baserel_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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extern double get_parameterized_baserel_size(PlannerInfo *root,
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RelOptInfo *rel,
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List *param_clauses);
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extern double get_parameterized_joinrel_size(PlannerInfo *root,
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RelOptInfo *rel,
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double outer_rows,
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double inner_rows,
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SpecialJoinInfo *sjinfo,
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List *restrict_clauses);
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extern void set_joinrel_size_estimates(PlannerInfo *root, RelOptInfo *rel,
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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 *restrictlist);
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extern void set_subquery_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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extern void set_function_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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extern void set_values_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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extern void set_cte_size_estimates(PlannerInfo *root, RelOptInfo *rel,
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Plan *cteplan);
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extern void set_foreign_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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/*
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* prototypes for clausesel.c
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* routines to compute clause selectivities
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*/
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extern Selectivity clauselist_selectivity(PlannerInfo *root,
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List *clauses,
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int varRelid,
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JoinType jointype,
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SpecialJoinInfo *sjinfo);
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extern Selectivity clause_selectivity(PlannerInfo *root,
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Node *clause,
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int varRelid,
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JoinType jointype,
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SpecialJoinInfo *sjinfo);
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#endif /* COST_H */
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