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564c19e86eff3f2221471e60a963d55bd5f76954
postgres/src/include/optimizer/pathnode.h
Tom Lane 564c19e86e Still more fixes for planner's handling of LATERAL references. 
More fuzz testing by Andreas Seltenreich exposed that the planner did not
cope well with chains of lateral references.  If relation X references Y
laterally, and Y references Z laterally, then we will have to scan X on the
inside of a nestloop with Z, so for all intents and purposes X is laterally
dependent on Z too.  The planner did not understand this and would generate
intermediate joins that could not be used.  While that was usually harmless
except for wasting some planning cycles, under the right circumstances it
would lead to "failed to build any N-way joins" or "could not devise a
query plan" planner failures.

To fix that, convert the existing per-relation lateral_relids and
lateral_referencers relid sets into their transitive closures; that is,
they now show all relations on which a rel is directly or indirectly
laterally dependent.  This not only fixes the chained-reference problem
but allows some of the relevant tests to be made substantially simpler
and faster, since they can be reduced to simple bitmap manipulations
instead of searches of the LateralJoinInfo list.

Also, when a PlaceHolderVar that is due to be evaluated at a join contains
lateral references, we should treat those references as indirect lateral
dependencies of each of the join's base relations.  This prevents us from
trying to join any individual base relations to the lateral reference
source before the join is formed, which again cannot work.

Andreas' testing also exposed another oversight in the "dangerous
PlaceHolderVar" test added in commit 85e5e222b1.  Simply rejecting
unsafe join paths in joinpath.c is insufficient, because in some cases
we will end up rejecting *all* possible paths for a particular join, again
leading to "could not devise a query plan" failures.  The restriction has
to be known also to join_is_legal and its cohort functions, so that they
will not select a join for which that will happen.  I chose to move the
supporting logic into joinrels.c where the latter functions are.

Back-patch to 9.3 where LATERAL support was introduced.
2015-12-11 14:22:20 -05:00

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/*-------------------------------------------------------------------------
*
* pathnode.h
* prototypes for pathnode.c, relnode.c.
*
*
* Portions Copyright (c) 1996-2015, 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/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 Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer);
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);
extern BitmapHeapPath *create_bitmap_heap_path(PlannerInfo *root,
RelOptInfo *rel,
Path *bitmapqual,
Relids required_outer,
double loop_count);
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(RelOptInfo *rel, List *subpaths,
Relids required_outer);
extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
RelOptInfo *rel,
List *subpaths,
List *pathkeys,
Relids required_outer);
extern ResultPath *create_result_path(List *quals);
extern MaterialPath *create_material_path(RelOptInfo *rel, Path *subpath);
extern UniquePath *create_unique_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath, SpecialJoinInfo *sjinfo);
extern Path *create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel,
List *pathkeys, Relids required_outer);
extern Path *create_functionscan_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_ctescan_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,
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(Path *outer_path, Path *inner_path);
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,
SpecialJoinInfo *sjinfo,
SemiAntiJoinFactors *semifactors,
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,
SpecialJoinInfo *sjinfo,
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,
SpecialJoinInfo *sjinfo,
SemiAntiJoinFactors *semifactors,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
Relids required_outer,
List *hashclauses);
extern Path *reparameterize_path(PlannerInfo *root, Path *path,
Relids required_outer,
double loop_count);
/*
* prototypes for relnode.c
*/
extern void setup_simple_rel_arrays(PlannerInfo *root);
extern RelOptInfo *build_simple_rel(PlannerInfo *root, int relid,
RelOptKind reloptkind);
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 AppendRelInfo *find_childrel_appendrelinfo(PlannerInfo *root,
RelOptInfo *rel);
extern RelOptInfo *find_childrel_top_parent(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);
#endif /* PATHNODE_H */
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