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postgres/src/include/optimizer/pathnode.h
Alvaro Herrera 499be013de Support partition pruning at execution time 
Existing partition pruning is only able to work at plan time, for query
quals that appear in the parsed query.  This is good but limiting, as
there can be parameters that appear later that can be usefully used to
further prune partitions.

This commit adds support for pruning subnodes of Append which cannot
possibly contain any matching tuples, during execution, by evaluating
Params to determine the minimum set of subnodes that can possibly match.
We support more than just simple Params in WHERE clauses. Support
additionally includes:

1. Parameterized Nested Loop Joins: The parameter from the outer side of the
   join can be used to determine the minimum set of inner side partitions to
   scan.

2. Initplans: Once an initplan has been executed we can then determine which
   partitions match the value from the initplan.

Partition pruning is performed in two ways.  When Params external to the plan
are found to match the partition key we attempt to prune away unneeded Append
subplans during the initialization of the executor.  This allows us to bypass
the initialization of non-matching subplans meaning they won't appear in the
EXPLAIN or EXPLAIN ANALYZE output.

For parameters whose value is only known during the actual execution
then the pruning of these subplans must wait.  Subplans which are
eliminated during this stage of pruning are still visible in the EXPLAIN
output.  In order to determine if pruning has actually taken place, the
EXPLAIN ANALYZE must be viewed.  If a certain Append subplan was never
executed due to the elimination of the partition then the execution
timing area will state "(never executed)".  Whereas, if, for example in
the case of parameterized nested loops, the number of loops stated in
the EXPLAIN ANALYZE output for certain subplans may appear lower than
others due to the subplan having been scanned fewer times.  This is due
to the list of matching subnodes having to be evaluated whenever a
parameter which was found to match the partition key changes.

This commit required some additional infrastructure that permits the
building of a data structure which is able to perform the translation of
the matching partition IDs, as returned by get_matching_partitions, into
the list index of a subpaths list, as exist in node types such as
Append, MergeAppend and ModifyTable.  This allows us to translate a list
of clauses into a Bitmapset of all the subpath indexes which must be
included to satisfy the clause list.

Author: David Rowley, based on an earlier effort by Beena Emerson
Reviewers: Amit Langote, Robert Haas, Amul Sul, Rajkumar Raghuwanshi,
Jesper Pedersen
Discussion: https://postgr.es/m/CAOG9ApE16ac-_VVZVvv0gePSgkg_BwYEV1NBqZFqDR2bBE0X0A@mail.gmail.com
2018-04-07 17:54:39 -03:00

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/*-------------------------------------------------------------------------
*
* pathnode.h
* prototypes for pathnode.c, relnode.c.
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/optimizer/pathnode.h
*
*-------------------------------------------------------------------------
*/
#ifndef PATHNODE_H
#define PATHNODE_H
#include "nodes/bitmapset.h"
#include "nodes/relation.h"
/*
* prototypes for pathnode.c
*/
extern int compare_path_costs(Path *path1, Path *path2,
CostSelector criterion);
extern int compare_fractional_path_costs(Path *path1, Path *path2,
double fraction);
extern void set_cheapest(RelOptInfo *parent_rel);
extern void add_path(RelOptInfo *parent_rel, Path *new_path);
extern bool add_path_precheck(RelOptInfo *parent_rel,
Cost startup_cost, Cost total_cost,
List *pathkeys, Relids required_outer);
extern void add_partial_path(RelOptInfo *parent_rel, Path *new_path);
extern bool add_partial_path_precheck(RelOptInfo *parent_rel,
Cost total_cost, List *pathkeys);
extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer, int parallel_workers);
extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern IndexPath *create_index_path(PlannerInfo *root,
IndexOptInfo *index,
List *indexclauses,
List *indexclausecols,
List *indexorderbys,
List *indexorderbycols,
List *pathkeys,
ScanDirection indexscandir,
bool indexonly,
Relids required_outer,
double loop_count,
bool partial_path);
extern BitmapHeapPath *create_bitmap_heap_path(PlannerInfo *root,
RelOptInfo *rel,
Path *bitmapqual,
Relids required_outer,
double loop_count,
int parallel_degree);
extern BitmapAndPath *create_bitmap_and_path(PlannerInfo *root,
RelOptInfo *rel,
List *bitmapquals);
extern BitmapOrPath *create_bitmap_or_path(PlannerInfo *root,
RelOptInfo *rel,
List *bitmapquals);
extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
List *tidquals, Relids required_outer);
extern AppendPath *create_append_path(PlannerInfo *root, RelOptInfo *rel,
List *subpaths, List *partial_subpaths,
Relids required_outer,
int parallel_workers, bool parallel_aware,
List *partitioned_rels, double rows);
extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
RelOptInfo *rel,
List *subpaths,
List *pathkeys,
Relids required_outer,
List *partitioned_rels);
extern ResultPath *create_result_path(PlannerInfo *root, RelOptInfo *rel,
PathTarget *target, List *resconstantqual);
extern MaterialPath *create_material_path(RelOptInfo *rel, Path *subpath);
extern UniquePath *create_unique_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath, SpecialJoinInfo *sjinfo);
extern GatherPath *create_gather_path(PlannerInfo *root,
RelOptInfo *rel, Path *subpath, PathTarget *target,
Relids required_outer, double *rows);
extern GatherMergePath *create_gather_merge_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
List *pathkeys,
Relids required_outer,
double *rows);
extern SubqueryScanPath *create_subqueryscan_path(PlannerInfo *root,
RelOptInfo *rel, Path *subpath,
List *pathkeys, Relids required_outer);
extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
List *pathkeys, Relids required_outer);
extern Path *create_tablexprscan_path(PlannerInfo *root, RelOptInfo *rel,
List *pathkeys, Relids required_outer);
extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern Path *create_tablefuncscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern Path *create_namedtuplestorescan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
PathTarget *target,
double rows, Cost startup_cost, Cost total_cost,
List *pathkeys,
Relids required_outer,
Path *fdw_outerpath,
List *fdw_private);
extern Relids calc_nestloop_required_outer(Relids outerrelids,
Relids outer_paramrels,
Relids innerrelids,
Relids inner_paramrels);
extern Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path);
extern NestPath *create_nestloop_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
JoinPathExtraData *extra,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
List *pathkeys,
Relids required_outer);
extern MergePath *create_mergejoin_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
JoinPathExtraData *extra,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
List *pathkeys,
Relids required_outer,
List *mergeclauses,
List *outersortkeys,
List *innersortkeys);
extern HashPath *create_hashjoin_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
JoinPathExtraData *extra,
Path *outer_path,
Path *inner_path,
bool parallel_hash,
List *restrict_clauses,
Relids required_outer,
List *hashclauses);
extern ProjectionPath *create_projection_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target);
extern Path *apply_projection_to_path(PlannerInfo *root,
RelOptInfo *rel,
Path *path,
PathTarget *target);
extern ProjectSetPath *create_set_projection_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target);
extern SortPath *create_sort_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
List *pathkeys,
double limit_tuples);
extern GroupPath *create_group_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
List *groupClause,
List *qual,
double numGroups);
extern UpperUniquePath *create_upper_unique_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
int numCols,
double numGroups);
extern AggPath *create_agg_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
AggStrategy aggstrategy,
AggSplit aggsplit,
List *groupClause,
List *qual,
const AggClauseCosts *aggcosts,
double numGroups);
extern GroupingSetsPath *create_groupingsets_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
List *having_qual,
AggStrategy aggstrategy,
List *rollups,
const AggClauseCosts *agg_costs,
double numGroups);
extern MinMaxAggPath *create_minmaxagg_path(PlannerInfo *root,
RelOptInfo *rel,
PathTarget *target,
List *mmaggregates,
List *quals);
extern WindowAggPath *create_windowagg_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
List *windowFuncs,
WindowClause *winclause,
List *winpathkeys);
extern SetOpPath *create_setop_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
SetOpCmd cmd,
SetOpStrategy strategy,
List *distinctList,
AttrNumber flagColIdx,
int firstFlag,
double numGroups,
double outputRows);
extern RecursiveUnionPath *create_recursiveunion_path(PlannerInfo *root,
RelOptInfo *rel,
Path *leftpath,
Path *rightpath,
PathTarget *target,
List *distinctList,
int wtParam,
double numGroups);
extern LockRowsPath *create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath, List *rowMarks, int epqParam);
extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
RelOptInfo *rel,
CmdType operation, bool canSetTag,
Index nominalRelation, List *partitioned_rels,
bool partColsUpdated,
List *resultRelations,
Index mergeTargetRelation,
List *subpaths,
List *subroots,
List *withCheckOptionLists, List *returningLists,
List *rowMarks, OnConflictExpr *onconflict,
List *mergeSourceTargetList,
List *mergeActionList, int epqParam);
extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
int64 offset_est, int64 count_est);
extern Path *reparameterize_path(PlannerInfo *root, Path *path,
Relids required_outer,
double loop_count);
extern Path *reparameterize_path_by_child(PlannerInfo *root, Path *path,
RelOptInfo *child_rel);
/*
* prototypes for relnode.c
*/
extern void setup_simple_rel_arrays(PlannerInfo *root);
extern RelOptInfo *build_simple_rel(PlannerInfo *root, int relid,
RelOptInfo *parent);
extern RelOptInfo *find_base_rel(PlannerInfo *root, int relid);
extern RelOptInfo *find_join_rel(PlannerInfo *root, Relids relids);
extern RelOptInfo *build_join_rel(PlannerInfo *root,
Relids joinrelids,
RelOptInfo *outer_rel,
RelOptInfo *inner_rel,
SpecialJoinInfo *sjinfo,
List **restrictlist_ptr);
extern Relids min_join_parameterization(PlannerInfo *root,
Relids joinrelids,
RelOptInfo *outer_rel,
RelOptInfo *inner_rel);
extern RelOptInfo *build_empty_join_rel(PlannerInfo *root);
extern RelOptInfo *fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind,
Relids relids);
extern AppendRelInfo *find_childrel_appendrelinfo(PlannerInfo *root,
RelOptInfo *rel);
extern Relids find_childrel_parents(PlannerInfo *root, RelOptInfo *rel);
extern ParamPathInfo *get_baserel_parampathinfo(PlannerInfo *root,
RelOptInfo *baserel,
Relids required_outer);
extern ParamPathInfo *get_joinrel_parampathinfo(PlannerInfo *root,
RelOptInfo *joinrel,
Path *outer_path,
Path *inner_path,
SpecialJoinInfo *sjinfo,
Relids required_outer,
List **restrict_clauses);
extern ParamPathInfo *get_appendrel_parampathinfo(RelOptInfo *appendrel,
Relids required_outer);
extern ParamPathInfo *find_param_path_info(RelOptInfo *rel,
Relids required_outer);
extern RelOptInfo *build_child_join_rel(PlannerInfo *root,
RelOptInfo *outer_rel, RelOptInfo *inner_rel,
RelOptInfo *parent_joinrel, List *restrictlist,
SpecialJoinInfo *sjinfo, JoinType jointype);
#endif /* PATHNODE_H */
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