14d8b539d3
WHERE EXISTS (...) queries cannot be executed by Parallel Hash Join with jointype JOIN_UNIQUE_INNER, because there is no way to make a partial plan totally unique. The consequence of allowing such plans was duplicate results from some EXISTS queries. Back-patch to 11. Bug #15857. Author: Thomas Munro Reviewed-by: Tom Lane Reported-by: Vladimir Kriukov Discussion: https://postgr.es/m/15857-d1ba2a64bce0795e%40postgresql.org
2030 lines
64 KiB
C
2030 lines
64 KiB
C
/*-------------------------------------------------------------------------
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*
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* joinpath.c
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* Routines to find all possible paths for processing a set of joins
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*
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* Portions Copyright (c) 1996-2018, 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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*
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* IDENTIFICATION
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* src/backend/optimizer/path/joinpath.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <math.h>
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#include "executor/executor.h"
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#include "foreign/fdwapi.h"
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#include "optimizer/cost.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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#include "optimizer/planmain.h"
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/* Hook for plugins to get control in add_paths_to_joinrel() */
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set_join_pathlist_hook_type set_join_pathlist_hook = NULL;
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/*
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* Paths parameterized by the parent can be considered to be parameterized by
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* any of its child.
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*/
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#define PATH_PARAM_BY_PARENT(path, rel) \
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((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), \
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(rel)->top_parent_relids))
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#define PATH_PARAM_BY_REL_SELF(path, rel) \
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((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), (rel)->relids))
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#define PATH_PARAM_BY_REL(path, rel) \
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(PATH_PARAM_BY_REL_SELF(path, rel) || PATH_PARAM_BY_PARENT(path, rel))
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static void try_partial_mergejoin_path(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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List *pathkeys,
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List *mergeclauses,
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List *outersortkeys,
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List *innersortkeys,
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JoinType jointype,
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JoinPathExtraData *extra);
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static void sort_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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JoinType jointype, JoinPathExtraData *extra);
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static void match_unsorted_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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JoinType jointype, JoinPathExtraData *extra);
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static void consider_parallel_nestloop(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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JoinType jointype,
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JoinPathExtraData *extra);
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static void consider_parallel_mergejoin(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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JoinType jointype,
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JoinPathExtraData *extra,
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Path *inner_cheapest_total);
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static void hash_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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JoinType jointype, JoinPathExtraData *extra);
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static List *select_mergejoin_clauses(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *restrictlist,
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JoinType jointype,
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bool *mergejoin_allowed);
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static void generate_mergejoin_paths(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *innerrel,
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Path *outerpath,
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JoinType jointype,
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JoinPathExtraData *extra,
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bool useallclauses,
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Path *inner_cheapest_total,
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List *merge_pathkeys,
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bool is_partial);
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/*
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* add_paths_to_joinrel
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* Given a join relation and two component rels from which it can be made,
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* consider all possible paths that use the two component rels as outer
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* and inner rel respectively. Add these paths to the join rel's pathlist
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* if they survive comparison with other paths (and remove any existing
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* paths that are dominated by these paths).
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*
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* Modifies the pathlist field of the joinrel node to contain the best
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* paths found so far.
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*
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* jointype is not necessarily the same as sjinfo->jointype; it might be
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* "flipped around" if we are considering joining the rels in the opposite
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* direction from what's indicated in sjinfo.
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*
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* Also, this routine and others in this module accept the special JoinTypes
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* JOIN_UNIQUE_OUTER and JOIN_UNIQUE_INNER to indicate that we should
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* unique-ify the outer or inner relation and then apply a regular inner
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* join. These values are not allowed to propagate outside this module,
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* however. Path cost estimation code may need to recognize that it's
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* dealing with such a case --- the combination of nominal jointype INNER
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* with sjinfo->jointype == JOIN_SEMI indicates that.
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*/
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void
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add_paths_to_joinrel(PlannerInfo *root,
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RelOptInfo *joinrel,
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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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{
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JoinPathExtraData extra;
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bool mergejoin_allowed = true;
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ListCell *lc;
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Relids joinrelids;
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/*
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* PlannerInfo doesn't contain the SpecialJoinInfos created for joins
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* between child relations, even if there is a SpecialJoinInfo node for
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* the join between the topmost parents. So, while calculating Relids set
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* representing the restriction, consider relids of topmost parent of
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* partitions.
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*/
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if (joinrel->reloptkind == RELOPT_OTHER_JOINREL)
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joinrelids = joinrel->top_parent_relids;
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else
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joinrelids = joinrel->relids;
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extra.restrictlist = restrictlist;
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extra.mergeclause_list = NIL;
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extra.sjinfo = sjinfo;
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extra.param_source_rels = NULL;
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/*
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* See if the inner relation is provably unique for this outer rel.
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*
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* We have some special cases: for JOIN_SEMI and JOIN_ANTI, it doesn't
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* matter since the executor can make the equivalent optimization anyway;
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* we need not expend planner cycles on proofs. For JOIN_UNIQUE_INNER, we
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* must be considering a semijoin whose inner side is not provably unique
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* (else reduce_unique_semijoins would've simplified it), so there's no
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* point in calling innerrel_is_unique. However, if the LHS covers all of
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* the semijoin's min_lefthand, then it's appropriate to set inner_unique
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* because the path produced by create_unique_path will be unique relative
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* to the LHS. (If we have an LHS that's only part of the min_lefthand,
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* that is *not* true.) For JOIN_UNIQUE_OUTER, pass JOIN_INNER to avoid
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* letting that value escape this module.
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*/
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switch (jointype)
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{
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case JOIN_SEMI:
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case JOIN_ANTI:
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extra.inner_unique = false; /* well, unproven */
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break;
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case JOIN_UNIQUE_INNER:
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extra.inner_unique = bms_is_subset(sjinfo->min_lefthand,
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outerrel->relids);
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break;
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case JOIN_UNIQUE_OUTER:
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extra.inner_unique = innerrel_is_unique(root,
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joinrel->relids,
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outerrel->relids,
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innerrel,
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JOIN_INNER,
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restrictlist,
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false);
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break;
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default:
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extra.inner_unique = innerrel_is_unique(root,
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joinrel->relids,
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outerrel->relids,
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innerrel,
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jointype,
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restrictlist,
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false);
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break;
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}
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/*
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* Find potential mergejoin clauses. We can skip this if we are not
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* interested in doing a mergejoin. However, mergejoin may be our only
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* way of implementing a full outer join, so override enable_mergejoin if
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* it's a full join.
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*/
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if (enable_mergejoin || jointype == JOIN_FULL)
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extra.mergeclause_list = select_mergejoin_clauses(root,
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joinrel,
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outerrel,
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innerrel,
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restrictlist,
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jointype,
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&mergejoin_allowed);
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/*
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* If it's SEMI, ANTI, or inner_unique join, compute correction factors
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* for cost estimation. These will be the same for all paths.
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*/
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if (jointype == JOIN_SEMI || jointype == JOIN_ANTI || extra.inner_unique)
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compute_semi_anti_join_factors(root, joinrel, outerrel, innerrel,
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jointype, sjinfo, restrictlist,
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&extra.semifactors);
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/*
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* Decide whether it's sensible to generate parameterized paths for this
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* joinrel, and if so, which relations such paths should require. There
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* is usually no need to create a parameterized result path unless there
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* is a join order restriction that prevents joining one of our input rels
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* directly to the parameter source rel instead of joining to the other
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* input rel. (But see allow_star_schema_join().) This restriction
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* reduces the number of parameterized paths we have to deal with at
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* higher join levels, without compromising the quality of the resulting
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* plan. We express the restriction as a Relids set that must overlap the
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* parameterization of any proposed join path.
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*/
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foreach(lc, root->join_info_list)
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{
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SpecialJoinInfo *sjinfo2 = (SpecialJoinInfo *) lfirst(lc);
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/*
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* SJ is relevant to this join if we have some part of its RHS
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* (possibly not all of it), and haven't yet joined to its LHS. (This
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* test is pretty simplistic, but should be sufficient considering the
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* join has already been proven legal.) If the SJ is relevant, it
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* presents constraints for joining to anything not in its RHS.
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*/
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if (bms_overlap(joinrelids, sjinfo2->min_righthand) &&
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!bms_overlap(joinrelids, sjinfo2->min_lefthand))
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extra.param_source_rels = bms_join(extra.param_source_rels,
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bms_difference(root->all_baserels,
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sjinfo2->min_righthand));
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/* full joins constrain both sides symmetrically */
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if (sjinfo2->jointype == JOIN_FULL &&
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bms_overlap(joinrelids, sjinfo2->min_lefthand) &&
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!bms_overlap(joinrelids, sjinfo2->min_righthand))
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extra.param_source_rels = bms_join(extra.param_source_rels,
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bms_difference(root->all_baserels,
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sjinfo2->min_lefthand));
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}
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/*
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* However, when a LATERAL subquery is involved, there will simply not be
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* any paths for the joinrel that aren't parameterized by whatever the
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* subquery is parameterized by, unless its parameterization is resolved
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* within the joinrel. So we might as well allow additional dependencies
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* on whatever residual lateral dependencies the joinrel will have.
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*/
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extra.param_source_rels = bms_add_members(extra.param_source_rels,
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joinrel->lateral_relids);
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/*
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* 1. Consider mergejoin paths where both relations must be explicitly
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* sorted. Skip this if we can't mergejoin.
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*/
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if (mergejoin_allowed)
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sort_inner_and_outer(root, joinrel, outerrel, innerrel,
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jointype, &extra);
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/*
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* 2. Consider paths where the outer relation need not be explicitly
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* sorted. This includes both nestloops and mergejoins where the outer
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* path is already ordered. Again, skip this if we can't mergejoin.
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* (That's okay because we know that nestloop can't handle right/full
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* joins at all, so it wouldn't work in the prohibited cases either.)
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*/
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if (mergejoin_allowed)
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match_unsorted_outer(root, joinrel, outerrel, innerrel,
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jointype, &extra);
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#ifdef NOT_USED
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/*
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* 3. Consider paths where the inner relation need not be explicitly
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* sorted. This includes mergejoins only (nestloops were already built in
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* match_unsorted_outer).
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*
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* Diked out as redundant 2/13/2000 -- tgl. There isn't any really
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* significant difference between the inner and outer side of a mergejoin,
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* so match_unsorted_inner creates no paths that aren't equivalent to
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* those made by match_unsorted_outer when add_paths_to_joinrel() is
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* invoked with the two rels given in the other order.
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*/
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if (mergejoin_allowed)
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match_unsorted_inner(root, joinrel, outerrel, innerrel,
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jointype, &extra);
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#endif
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/*
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* 4. Consider paths where both outer and inner relations must be hashed
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* before being joined. As above, disregard enable_hashjoin for full
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* joins, because there may be no other alternative.
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*/
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if (enable_hashjoin || jointype == JOIN_FULL)
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hash_inner_and_outer(root, joinrel, outerrel, innerrel,
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jointype, &extra);
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/*
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* 5. If inner and outer relations are foreign tables (or joins) belonging
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* to the same server and assigned to the same user to check access
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* permissions as, give the FDW a chance to push down joins.
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*/
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if (joinrel->fdwroutine &&
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joinrel->fdwroutine->GetForeignJoinPaths)
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joinrel->fdwroutine->GetForeignJoinPaths(root, joinrel,
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outerrel, innerrel,
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jointype, &extra);
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/*
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* 6. Finally, give extensions a chance to manipulate the path list.
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*/
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if (set_join_pathlist_hook)
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set_join_pathlist_hook(root, joinrel, outerrel, innerrel,
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jointype, &extra);
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}
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/*
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* We override the param_source_rels heuristic to accept nestloop paths in
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* which the outer rel satisfies some but not all of the inner path's
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* parameterization. This is necessary to get good plans for star-schema
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* scenarios, in which a parameterized path for a large table may require
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* parameters from multiple small tables that will not get joined directly to
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* each other. We can handle that by stacking nestloops that have the small
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* tables on the outside; but this breaks the rule the param_source_rels
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* heuristic is based on, namely that parameters should not be passed down
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* across joins unless there's a join-order-constraint-based reason to do so.
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* So we ignore the param_source_rels restriction when this case applies.
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*
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* allow_star_schema_join() returns true if the param_source_rels restriction
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* should be overridden, ie, it's okay to perform this join.
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*/
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static inline bool
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allow_star_schema_join(PlannerInfo *root,
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Relids outerrelids,
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Relids inner_paramrels)
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{
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/*
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* It's a star-schema case if the outer rel provides some but not all of
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* the inner rel's parameterization.
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*/
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return (bms_overlap(inner_paramrels, outerrelids) &&
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bms_nonempty_difference(inner_paramrels, outerrelids));
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}
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/*
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* try_nestloop_path
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* Consider a nestloop join path; if it appears useful, push it into
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* the joinrel's pathlist via add_path().
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*/
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static void
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try_nestloop_path(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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List *pathkeys,
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JoinType jointype,
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JoinPathExtraData *extra)
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{
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Relids required_outer;
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JoinCostWorkspace workspace;
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RelOptInfo *innerrel = inner_path->parent;
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RelOptInfo *outerrel = outer_path->parent;
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Relids innerrelids;
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Relids outerrelids;
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Relids inner_paramrels = PATH_REQ_OUTER(inner_path);
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Relids outer_paramrels = PATH_REQ_OUTER(outer_path);
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/*
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* Paths are parameterized by top-level parents, so run parameterization
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* tests on the parent relids.
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*/
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if (innerrel->top_parent_relids)
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innerrelids = innerrel->top_parent_relids;
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else
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innerrelids = innerrel->relids;
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if (outerrel->top_parent_relids)
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outerrelids = outerrel->top_parent_relids;
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else
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outerrelids = outerrel->relids;
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/*
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* Check to see if proposed path is still parameterized, and reject if the
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* parameterization wouldn't be sensible --- unless allow_star_schema_join
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* says to allow it anyway. Also, we must reject if have_dangerous_phv
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* doesn't like the look of it, which could only happen if the nestloop is
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* still parameterized.
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*/
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required_outer = calc_nestloop_required_outer(outerrelids, outer_paramrels,
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innerrelids, inner_paramrels);
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if (required_outer &&
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((!bms_overlap(required_outer, extra->param_source_rels) &&
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!allow_star_schema_join(root, outerrelids, inner_paramrels)) ||
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have_dangerous_phv(root, outerrelids, inner_paramrels)))
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{
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/* Waste no memory when we reject a path here */
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bms_free(required_outer);
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return;
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}
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/*
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* Do a precheck to quickly eliminate obviously-inferior paths. We
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* calculate a cheap lower bound on the path's cost and then use
|
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* add_path_precheck() to see if the path is clearly going to be dominated
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* by some existing path for the joinrel. If not, do the full pushup with
|
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* creating a fully valid path structure and submitting it to add_path().
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* The latter two steps are expensive enough to make this two-phase
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* methodology worthwhile.
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*/
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initial_cost_nestloop(root, &workspace, jointype,
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outer_path, inner_path, extra);
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if (add_path_precheck(joinrel,
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workspace.startup_cost, workspace.total_cost,
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pathkeys, required_outer))
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{
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/*
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* If the inner path is parameterized, it is parameterized by the
|
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* topmost parent of the outer rel, not the outer rel itself. Fix
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* that.
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*/
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if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent))
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{
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inner_path = reparameterize_path_by_child(root, inner_path,
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outer_path->parent);
|
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|
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/*
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* If we could not translate the path, we can't create nest loop
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* path.
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*/
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if (!inner_path)
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{
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bms_free(required_outer);
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return;
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}
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}
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add_path(joinrel, (Path *)
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create_nestloop_path(root,
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joinrel,
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jointype,
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&workspace,
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extra,
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outer_path,
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inner_path,
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extra->restrictlist,
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pathkeys,
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required_outer));
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}
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else
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{
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/* Waste no memory when we reject a path here */
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bms_free(required_outer);
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}
|
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}
|
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|
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/*
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* try_partial_nestloop_path
|
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* Consider a partial nestloop join path; if it appears useful, push it into
|
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* the joinrel's partial_pathlist via add_partial_path().
|
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*/
|
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static void
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try_partial_nestloop_path(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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List *pathkeys,
|
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JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinCostWorkspace workspace;
|
|
|
|
/*
|
|
* If the inner path is parameterized, the parameterization must be fully
|
|
* satisfied by the proposed outer path. Parameterized partial paths are
|
|
* not supported. The caller should already have verified that no
|
|
* extra_lateral_rels are required here.
|
|
*/
|
|
Assert(bms_is_empty(joinrel->lateral_relids));
|
|
if (inner_path->param_info != NULL)
|
|
{
|
|
Relids inner_paramrels = inner_path->param_info->ppi_req_outer;
|
|
RelOptInfo *outerrel = outer_path->parent;
|
|
Relids outerrelids;
|
|
|
|
/*
|
|
* The inner and outer paths are parameterized, if at all, by the top
|
|
* level parents, not the child relations, so we must use those relids
|
|
* for our parameterization tests.
|
|
*/
|
|
if (outerrel->top_parent_relids)
|
|
outerrelids = outerrel->top_parent_relids;
|
|
else
|
|
outerrelids = outerrel->relids;
|
|
|
|
if (!bms_is_subset(inner_paramrels, outerrelids))
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Before creating a path, get a quick lower bound on what it is likely to
|
|
* cost. Bail out right away if it looks terrible.
|
|
*/
|
|
initial_cost_nestloop(root, &workspace, jointype,
|
|
outer_path, inner_path, extra);
|
|
if (!add_partial_path_precheck(joinrel, workspace.total_cost, pathkeys))
|
|
return;
|
|
|
|
/*
|
|
* If the inner path is parameterized, it is parameterized by the topmost
|
|
* parent of the outer rel, not the outer rel itself. Fix that.
|
|
*/
|
|
if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent))
|
|
{
|
|
inner_path = reparameterize_path_by_child(root, inner_path,
|
|
outer_path->parent);
|
|
|
|
/*
|
|
* If we could not translate the path, we can't create nest loop path.
|
|
*/
|
|
if (!inner_path)
|
|
return;
|
|
}
|
|
|
|
/* Might be good enough to be worth trying, so let's try it. */
|
|
add_partial_path(joinrel, (Path *)
|
|
create_nestloop_path(root,
|
|
joinrel,
|
|
jointype,
|
|
&workspace,
|
|
extra,
|
|
outer_path,
|
|
inner_path,
|
|
extra->restrictlist,
|
|
pathkeys,
|
|
NULL));
|
|
}
|
|
|
|
/*
|
|
* try_mergejoin_path
|
|
* Consider a merge join path; if it appears useful, push it into
|
|
* the joinrel's pathlist via add_path().
|
|
*/
|
|
static void
|
|
try_mergejoin_path(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
Path *outer_path,
|
|
Path *inner_path,
|
|
List *pathkeys,
|
|
List *mergeclauses,
|
|
List *outersortkeys,
|
|
List *innersortkeys,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra,
|
|
bool is_partial)
|
|
{
|
|
Relids required_outer;
|
|
JoinCostWorkspace workspace;
|
|
|
|
if (is_partial)
|
|
{
|
|
try_partial_mergejoin_path(root,
|
|
joinrel,
|
|
outer_path,
|
|
inner_path,
|
|
pathkeys,
|
|
mergeclauses,
|
|
outersortkeys,
|
|
innersortkeys,
|
|
jointype,
|
|
extra);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Check to see if proposed path is still parameterized, and reject if the
|
|
* parameterization wouldn't be sensible.
|
|
*/
|
|
required_outer = calc_non_nestloop_required_outer(outer_path,
|
|
inner_path);
|
|
if (required_outer &&
|
|
!bms_overlap(required_outer, extra->param_source_rels))
|
|
{
|
|
/* Waste no memory when we reject a path here */
|
|
bms_free(required_outer);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If the given paths are already well enough ordered, we can skip doing
|
|
* an explicit sort.
|
|
*/
|
|
if (outersortkeys &&
|
|
pathkeys_contained_in(outersortkeys, outer_path->pathkeys))
|
|
outersortkeys = NIL;
|
|
if (innersortkeys &&
|
|
pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
|
|
innersortkeys = NIL;
|
|
|
|
/*
|
|
* See comments in try_nestloop_path().
|
|
*/
|
|
initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
|
|
outer_path, inner_path,
|
|
outersortkeys, innersortkeys,
|
|
extra);
|
|
|
|
if (add_path_precheck(joinrel,
|
|
workspace.startup_cost, workspace.total_cost,
|
|
pathkeys, required_outer))
|
|
{
|
|
add_path(joinrel, (Path *)
|
|
create_mergejoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
&workspace,
|
|
extra,
|
|
outer_path,
|
|
inner_path,
|
|
extra->restrictlist,
|
|
pathkeys,
|
|
required_outer,
|
|
mergeclauses,
|
|
outersortkeys,
|
|
innersortkeys));
|
|
}
|
|
else
|
|
{
|
|
/* Waste no memory when we reject a path here */
|
|
bms_free(required_outer);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* try_partial_mergejoin_path
|
|
* Consider a partial merge join path; if it appears useful, push it into
|
|
* the joinrel's pathlist via add_partial_path().
|
|
*/
|
|
static void
|
|
try_partial_mergejoin_path(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
Path *outer_path,
|
|
Path *inner_path,
|
|
List *pathkeys,
|
|
List *mergeclauses,
|
|
List *outersortkeys,
|
|
List *innersortkeys,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinCostWorkspace workspace;
|
|
|
|
/*
|
|
* See comments in try_partial_hashjoin_path().
|
|
*/
|
|
Assert(bms_is_empty(joinrel->lateral_relids));
|
|
if (inner_path->param_info != NULL)
|
|
{
|
|
Relids inner_paramrels = inner_path->param_info->ppi_req_outer;
|
|
|
|
if (!bms_is_empty(inner_paramrels))
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If the given paths are already well enough ordered, we can skip doing
|
|
* an explicit sort.
|
|
*/
|
|
if (outersortkeys &&
|
|
pathkeys_contained_in(outersortkeys, outer_path->pathkeys))
|
|
outersortkeys = NIL;
|
|
if (innersortkeys &&
|
|
pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
|
|
innersortkeys = NIL;
|
|
|
|
/*
|
|
* See comments in try_partial_nestloop_path().
|
|
*/
|
|
initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
|
|
outer_path, inner_path,
|
|
outersortkeys, innersortkeys,
|
|
extra);
|
|
|
|
if (!add_partial_path_precheck(joinrel, workspace.total_cost, pathkeys))
|
|
return;
|
|
|
|
/* Might be good enough to be worth trying, so let's try it. */
|
|
add_partial_path(joinrel, (Path *)
|
|
create_mergejoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
&workspace,
|
|
extra,
|
|
outer_path,
|
|
inner_path,
|
|
extra->restrictlist,
|
|
pathkeys,
|
|
NULL,
|
|
mergeclauses,
|
|
outersortkeys,
|
|
innersortkeys));
|
|
}
|
|
|
|
/*
|
|
* try_hashjoin_path
|
|
* Consider a hash join path; if it appears useful, push it into
|
|
* the joinrel's pathlist via add_path().
|
|
*/
|
|
static void
|
|
try_hashjoin_path(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
Path *outer_path,
|
|
Path *inner_path,
|
|
List *hashclauses,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
Relids required_outer;
|
|
JoinCostWorkspace workspace;
|
|
|
|
/*
|
|
* Check to see if proposed path is still parameterized, and reject if the
|
|
* parameterization wouldn't be sensible.
|
|
*/
|
|
required_outer = calc_non_nestloop_required_outer(outer_path,
|
|
inner_path);
|
|
if (required_outer &&
|
|
!bms_overlap(required_outer, extra->param_source_rels))
|
|
{
|
|
/* Waste no memory when we reject a path here */
|
|
bms_free(required_outer);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* See comments in try_nestloop_path(). Also note that hashjoin paths
|
|
* never have any output pathkeys, per comments in create_hashjoin_path.
|
|
*/
|
|
initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
|
|
outer_path, inner_path, extra, false);
|
|
|
|
if (add_path_precheck(joinrel,
|
|
workspace.startup_cost, workspace.total_cost,
|
|
NIL, required_outer))
|
|
{
|
|
add_path(joinrel, (Path *)
|
|
create_hashjoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
&workspace,
|
|
extra,
|
|
outer_path,
|
|
inner_path,
|
|
false, /* parallel_hash */
|
|
extra->restrictlist,
|
|
required_outer,
|
|
hashclauses));
|
|
}
|
|
else
|
|
{
|
|
/* Waste no memory when we reject a path here */
|
|
bms_free(required_outer);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* try_partial_hashjoin_path
|
|
* Consider a partial hashjoin join path; if it appears useful, push it into
|
|
* the joinrel's partial_pathlist via add_partial_path().
|
|
* The outer side is partial. If parallel_hash is true, then the inner path
|
|
* must be partial and will be run in parallel to create one or more shared
|
|
* hash tables; otherwise the inner path must be complete and a copy of it
|
|
* is run in every process to create separate identical private hash tables.
|
|
*/
|
|
static void
|
|
try_partial_hashjoin_path(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
Path *outer_path,
|
|
Path *inner_path,
|
|
List *hashclauses,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra,
|
|
bool parallel_hash)
|
|
{
|
|
JoinCostWorkspace workspace;
|
|
|
|
/*
|
|
* If the inner path is parameterized, the parameterization must be fully
|
|
* satisfied by the proposed outer path. Parameterized partial paths are
|
|
* not supported. The caller should already have verified that no
|
|
* extra_lateral_rels are required here.
|
|
*/
|
|
Assert(bms_is_empty(joinrel->lateral_relids));
|
|
if (inner_path->param_info != NULL)
|
|
{
|
|
Relids inner_paramrels = inner_path->param_info->ppi_req_outer;
|
|
|
|
if (!bms_is_empty(inner_paramrels))
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Before creating a path, get a quick lower bound on what it is likely to
|
|
* cost. Bail out right away if it looks terrible.
|
|
*/
|
|
initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
|
|
outer_path, inner_path, extra, parallel_hash);
|
|
if (!add_partial_path_precheck(joinrel, workspace.total_cost, NIL))
|
|
return;
|
|
|
|
/* Might be good enough to be worth trying, so let's try it. */
|
|
add_partial_path(joinrel, (Path *)
|
|
create_hashjoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
&workspace,
|
|
extra,
|
|
outer_path,
|
|
inner_path,
|
|
parallel_hash,
|
|
extra->restrictlist,
|
|
NULL,
|
|
hashclauses));
|
|
}
|
|
|
|
/*
|
|
* clause_sides_match_join
|
|
* Determine whether a join clause is of the right form to use in this join.
|
|
*
|
|
* We already know that the clause is a binary opclause referencing only the
|
|
* rels in the current join. The point here is to check whether it has the
|
|
* form "outerrel_expr op innerrel_expr" or "innerrel_expr op outerrel_expr",
|
|
* rather than mixing outer and inner vars on either side. If it matches,
|
|
* we set the transient flag outer_is_left to identify which side is which.
|
|
*/
|
|
static inline bool
|
|
clause_sides_match_join(RestrictInfo *rinfo, RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel)
|
|
{
|
|
if (bms_is_subset(rinfo->left_relids, outerrel->relids) &&
|
|
bms_is_subset(rinfo->right_relids, innerrel->relids))
|
|
{
|
|
/* lefthand side is outer */
|
|
rinfo->outer_is_left = true;
|
|
return true;
|
|
}
|
|
else if (bms_is_subset(rinfo->left_relids, innerrel->relids) &&
|
|
bms_is_subset(rinfo->right_relids, outerrel->relids))
|
|
{
|
|
/* righthand side is outer */
|
|
rinfo->outer_is_left = false;
|
|
return true;
|
|
}
|
|
return false; /* no good for these input relations */
|
|
}
|
|
|
|
/*
|
|
* sort_inner_and_outer
|
|
* Create mergejoin join paths by explicitly sorting both the outer and
|
|
* inner join relations on each available merge ordering.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'jointype' is the type of join to do
|
|
* 'extra' contains additional input values
|
|
*/
|
|
static void
|
|
sort_inner_and_outer(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinType save_jointype = jointype;
|
|
Path *outer_path;
|
|
Path *inner_path;
|
|
Path *cheapest_partial_outer = NULL;
|
|
Path *cheapest_safe_inner = NULL;
|
|
List *all_pathkeys;
|
|
ListCell *l;
|
|
|
|
/*
|
|
* We only consider the cheapest-total-cost input paths, since we are
|
|
* assuming here that a sort is required. We will consider
|
|
* cheapest-startup-cost input paths later, and only if they don't need a
|
|
* sort.
|
|
*
|
|
* This function intentionally does not consider parameterized input
|
|
* paths, except when the cheapest-total is parameterized. If we did so,
|
|
* we'd have a combinatorial explosion of mergejoin paths of dubious
|
|
* value. This interacts with decisions elsewhere that also discriminate
|
|
* against mergejoins with parameterized inputs; see comments in
|
|
* src/backend/optimizer/README.
|
|
*/
|
|
outer_path = outerrel->cheapest_total_path;
|
|
inner_path = innerrel->cheapest_total_path;
|
|
|
|
/*
|
|
* If either cheapest-total path is parameterized by the other rel, we
|
|
* can't use a mergejoin. (There's no use looking for alternative input
|
|
* paths, since these should already be the least-parameterized available
|
|
* paths.)
|
|
*/
|
|
if (PATH_PARAM_BY_REL(outer_path, innerrel) ||
|
|
PATH_PARAM_BY_REL(inner_path, outerrel))
|
|
return;
|
|
|
|
/*
|
|
* If unique-ification is requested, do it and then handle as a plain
|
|
* inner join.
|
|
*/
|
|
if (jointype == JOIN_UNIQUE_OUTER)
|
|
{
|
|
outer_path = (Path *) create_unique_path(root, outerrel,
|
|
outer_path, extra->sjinfo);
|
|
Assert(outer_path);
|
|
jointype = JOIN_INNER;
|
|
}
|
|
else if (jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
inner_path = (Path *) create_unique_path(root, innerrel,
|
|
inner_path, extra->sjinfo);
|
|
Assert(inner_path);
|
|
jointype = JOIN_INNER;
|
|
}
|
|
|
|
/*
|
|
* If the joinrel is parallel-safe, we may be able to consider a partial
|
|
* merge join. However, we can't handle JOIN_UNIQUE_OUTER, because the
|
|
* outer path will be partial, and therefore we won't be able to properly
|
|
* guarantee uniqueness. Similarly, we can't handle JOIN_FULL and
|
|
* JOIN_RIGHT, because they can produce false null extended rows. Also,
|
|
* the resulting path must not be parameterized.
|
|
*/
|
|
if (joinrel->consider_parallel &&
|
|
save_jointype != JOIN_UNIQUE_OUTER &&
|
|
save_jointype != JOIN_FULL &&
|
|
save_jointype != JOIN_RIGHT &&
|
|
outerrel->partial_pathlist != NIL &&
|
|
bms_is_empty(joinrel->lateral_relids))
|
|
{
|
|
cheapest_partial_outer = (Path *) linitial(outerrel->partial_pathlist);
|
|
|
|
if (inner_path->parallel_safe)
|
|
cheapest_safe_inner = inner_path;
|
|
else if (save_jointype != JOIN_UNIQUE_INNER)
|
|
cheapest_safe_inner =
|
|
get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
|
|
}
|
|
|
|
/*
|
|
* Each possible ordering of the available mergejoin clauses will generate
|
|
* a differently-sorted result path at essentially the same cost. We have
|
|
* no basis for choosing one over another at this level of joining, but
|
|
* some sort orders may be more useful than others for higher-level
|
|
* mergejoins, so it's worth considering multiple orderings.
|
|
*
|
|
* Actually, it's not quite true that every mergeclause ordering will
|
|
* generate a different path order, because some of the clauses may be
|
|
* partially redundant (refer to the same EquivalenceClasses). Therefore,
|
|
* what we do is convert the mergeclause list to a list of canonical
|
|
* pathkeys, and then consider different orderings of the pathkeys.
|
|
*
|
|
* Generating a path for *every* permutation of the pathkeys doesn't seem
|
|
* like a winning strategy; the cost in planning time is too high. For
|
|
* now, we generate one path for each pathkey, listing that pathkey first
|
|
* and the rest in random order. This should allow at least a one-clause
|
|
* mergejoin without re-sorting against any other possible mergejoin
|
|
* partner path. But if we've not guessed the right ordering of secondary
|
|
* keys, we may end up evaluating clauses as qpquals when they could have
|
|
* been done as mergeclauses. (In practice, it's rare that there's more
|
|
* than two or three mergeclauses, so expending a huge amount of thought
|
|
* on that is probably not worth it.)
|
|
*
|
|
* The pathkey order returned by select_outer_pathkeys_for_merge() has
|
|
* some heuristics behind it (see that function), so be sure to try it
|
|
* exactly as-is as well as making variants.
|
|
*/
|
|
all_pathkeys = select_outer_pathkeys_for_merge(root,
|
|
extra->mergeclause_list,
|
|
joinrel);
|
|
|
|
foreach(l, all_pathkeys)
|
|
{
|
|
List *front_pathkey = (List *) lfirst(l);
|
|
List *cur_mergeclauses;
|
|
List *outerkeys;
|
|
List *innerkeys;
|
|
List *merge_pathkeys;
|
|
|
|
/* Make a pathkey list with this guy first */
|
|
if (l != list_head(all_pathkeys))
|
|
outerkeys = lcons(front_pathkey,
|
|
list_delete_ptr(list_copy(all_pathkeys),
|
|
front_pathkey));
|
|
else
|
|
outerkeys = all_pathkeys; /* no work at first one... */
|
|
|
|
/* Sort the mergeclauses into the corresponding ordering */
|
|
cur_mergeclauses =
|
|
find_mergeclauses_for_outer_pathkeys(root,
|
|
outerkeys,
|
|
extra->mergeclause_list);
|
|
|
|
/* Should have used them all... */
|
|
Assert(list_length(cur_mergeclauses) == list_length(extra->mergeclause_list));
|
|
|
|
/* Build sort pathkeys for the inner side */
|
|
innerkeys = make_inner_pathkeys_for_merge(root,
|
|
cur_mergeclauses,
|
|
outerkeys);
|
|
|
|
/* Build pathkeys representing output sort order */
|
|
merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
|
|
outerkeys);
|
|
|
|
/*
|
|
* And now we can make the path.
|
|
*
|
|
* Note: it's possible that the cheapest paths will already be sorted
|
|
* properly. try_mergejoin_path will detect that case and suppress an
|
|
* explicit sort step, so we needn't do so here.
|
|
*/
|
|
try_mergejoin_path(root,
|
|
joinrel,
|
|
outer_path,
|
|
inner_path,
|
|
merge_pathkeys,
|
|
cur_mergeclauses,
|
|
outerkeys,
|
|
innerkeys,
|
|
jointype,
|
|
extra,
|
|
false);
|
|
|
|
/*
|
|
* If we have partial outer and parallel safe inner path then try
|
|
* partial mergejoin path.
|
|
*/
|
|
if (cheapest_partial_outer && cheapest_safe_inner)
|
|
try_partial_mergejoin_path(root,
|
|
joinrel,
|
|
cheapest_partial_outer,
|
|
cheapest_safe_inner,
|
|
merge_pathkeys,
|
|
cur_mergeclauses,
|
|
outerkeys,
|
|
innerkeys,
|
|
jointype,
|
|
extra);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* generate_mergejoin_paths
|
|
* Creates possible mergejoin paths for input outerpath.
|
|
*
|
|
* We generate mergejoins if mergejoin clauses are available. We have
|
|
* two ways to generate the inner path for a mergejoin: sort the cheapest
|
|
* inner path, or use an inner path that is already suitably ordered for the
|
|
* merge. If we have several mergeclauses, it could be that there is no inner
|
|
* path (or only a very expensive one) for the full list of mergeclauses, but
|
|
* better paths exist if we truncate the mergeclause list (thereby discarding
|
|
* some sort key requirements). So, we consider truncations of the
|
|
* mergeclause list as well as the full list. (Ideally we'd consider all
|
|
* subsets of the mergeclause list, but that seems way too expensive.)
|
|
*/
|
|
static void
|
|
generate_mergejoin_paths(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *innerrel,
|
|
Path *outerpath,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra,
|
|
bool useallclauses,
|
|
Path *inner_cheapest_total,
|
|
List *merge_pathkeys,
|
|
bool is_partial)
|
|
{
|
|
List *mergeclauses;
|
|
List *innersortkeys;
|
|
List *trialsortkeys;
|
|
Path *cheapest_startup_inner;
|
|
Path *cheapest_total_inner;
|
|
JoinType save_jointype = jointype;
|
|
int num_sortkeys;
|
|
int sortkeycnt;
|
|
|
|
if (jointype == JOIN_UNIQUE_OUTER || jointype == JOIN_UNIQUE_INNER)
|
|
jointype = JOIN_INNER;
|
|
|
|
/* Look for useful mergeclauses (if any) */
|
|
mergeclauses =
|
|
find_mergeclauses_for_outer_pathkeys(root,
|
|
outerpath->pathkeys,
|
|
extra->mergeclause_list);
|
|
|
|
/*
|
|
* Done with this outer path if no chance for a mergejoin.
|
|
*
|
|
* Special corner case: for "x FULL JOIN y ON true", there will be no join
|
|
* clauses at all. Ordinarily we'd generate a clauseless nestloop path,
|
|
* but since mergejoin is our only join type that supports FULL JOIN
|
|
* without any join clauses, it's necessary to generate a clauseless
|
|
* mergejoin path instead.
|
|
*/
|
|
if (mergeclauses == NIL)
|
|
{
|
|
if (jointype == JOIN_FULL)
|
|
/* okay to try for mergejoin */ ;
|
|
else
|
|
return;
|
|
}
|
|
if (useallclauses &&
|
|
list_length(mergeclauses) != list_length(extra->mergeclause_list))
|
|
return;
|
|
|
|
/* Compute the required ordering of the inner path */
|
|
innersortkeys = make_inner_pathkeys_for_merge(root,
|
|
mergeclauses,
|
|
outerpath->pathkeys);
|
|
|
|
/*
|
|
* Generate a mergejoin on the basis of sorting the cheapest inner. Since
|
|
* a sort will be needed, only cheapest total cost matters. (But
|
|
* try_mergejoin_path will do the right thing if inner_cheapest_total is
|
|
* already correctly sorted.)
|
|
*/
|
|
try_mergejoin_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
inner_cheapest_total,
|
|
merge_pathkeys,
|
|
mergeclauses,
|
|
NIL,
|
|
innersortkeys,
|
|
jointype,
|
|
extra,
|
|
is_partial);
|
|
|
|
/* Can't do anything else if inner path needs to be unique'd */
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
return;
|
|
|
|
/*
|
|
* Look for presorted inner paths that satisfy the innersortkey list ---
|
|
* or any truncation thereof, if we are allowed to build a mergejoin using
|
|
* a subset of the merge clauses. Here, we consider both cheap startup
|
|
* cost and cheap total cost.
|
|
*
|
|
* Currently we do not consider parameterized inner paths here. This
|
|
* interacts with decisions elsewhere that also discriminate against
|
|
* mergejoins with parameterized inputs; see comments in
|
|
* src/backend/optimizer/README.
|
|
*
|
|
* As we shorten the sortkey list, we should consider only paths that are
|
|
* strictly cheaper than (in particular, not the same as) any path found
|
|
* in an earlier iteration. Otherwise we'd be intentionally using fewer
|
|
* merge keys than a given path allows (treating the rest as plain
|
|
* joinquals), which is unlikely to be a good idea. Also, eliminating
|
|
* paths here on the basis of compare_path_costs is a lot cheaper than
|
|
* building the mergejoin path only to throw it away.
|
|
*
|
|
* If inner_cheapest_total is well enough sorted to have not required a
|
|
* sort in the path made above, we shouldn't make a duplicate path with
|
|
* it, either. We handle that case with the same logic that handles the
|
|
* previous consideration, by initializing the variables that track
|
|
* cheapest-so-far properly. Note that we do NOT reject
|
|
* inner_cheapest_total if we find it matches some shorter set of
|
|
* pathkeys. That case corresponds to using fewer mergekeys to avoid
|
|
* sorting inner_cheapest_total, whereas we did sort it above, so the
|
|
* plans being considered are different.
|
|
*/
|
|
if (pathkeys_contained_in(innersortkeys,
|
|
inner_cheapest_total->pathkeys))
|
|
{
|
|
/* inner_cheapest_total didn't require a sort */
|
|
cheapest_startup_inner = inner_cheapest_total;
|
|
cheapest_total_inner = inner_cheapest_total;
|
|
}
|
|
else
|
|
{
|
|
/* it did require a sort, at least for the full set of keys */
|
|
cheapest_startup_inner = NULL;
|
|
cheapest_total_inner = NULL;
|
|
}
|
|
num_sortkeys = list_length(innersortkeys);
|
|
if (num_sortkeys > 1 && !useallclauses)
|
|
trialsortkeys = list_copy(innersortkeys); /* need modifiable copy */
|
|
else
|
|
trialsortkeys = innersortkeys; /* won't really truncate */
|
|
|
|
for (sortkeycnt = num_sortkeys; sortkeycnt > 0; sortkeycnt--)
|
|
{
|
|
Path *innerpath;
|
|
List *newclauses = NIL;
|
|
|
|
/*
|
|
* Look for an inner path ordered well enough for the first
|
|
* 'sortkeycnt' innersortkeys. NB: trialsortkeys list is modified
|
|
* destructively, which is why we made a copy...
|
|
*/
|
|
trialsortkeys = list_truncate(trialsortkeys, sortkeycnt);
|
|
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
|
|
trialsortkeys,
|
|
NULL,
|
|
TOTAL_COST,
|
|
is_partial);
|
|
if (innerpath != NULL &&
|
|
(cheapest_total_inner == NULL ||
|
|
compare_path_costs(innerpath, cheapest_total_inner,
|
|
TOTAL_COST) < 0))
|
|
{
|
|
/* Found a cheap (or even-cheaper) sorted path */
|
|
/* Select the right mergeclauses, if we didn't already */
|
|
if (sortkeycnt < num_sortkeys)
|
|
{
|
|
newclauses =
|
|
trim_mergeclauses_for_inner_pathkeys(root,
|
|
mergeclauses,
|
|
trialsortkeys);
|
|
Assert(newclauses != NIL);
|
|
}
|
|
else
|
|
newclauses = mergeclauses;
|
|
try_mergejoin_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
innerpath,
|
|
merge_pathkeys,
|
|
newclauses,
|
|
NIL,
|
|
NIL,
|
|
jointype,
|
|
extra,
|
|
is_partial);
|
|
cheapest_total_inner = innerpath;
|
|
}
|
|
/* Same on the basis of cheapest startup cost ... */
|
|
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
|
|
trialsortkeys,
|
|
NULL,
|
|
STARTUP_COST,
|
|
is_partial);
|
|
if (innerpath != NULL &&
|
|
(cheapest_startup_inner == NULL ||
|
|
compare_path_costs(innerpath, cheapest_startup_inner,
|
|
STARTUP_COST) < 0))
|
|
{
|
|
/* Found a cheap (or even-cheaper) sorted path */
|
|
if (innerpath != cheapest_total_inner)
|
|
{
|
|
/*
|
|
* Avoid rebuilding clause list if we already made one; saves
|
|
* memory in big join trees...
|
|
*/
|
|
if (newclauses == NIL)
|
|
{
|
|
if (sortkeycnt < num_sortkeys)
|
|
{
|
|
newclauses =
|
|
trim_mergeclauses_for_inner_pathkeys(root,
|
|
mergeclauses,
|
|
trialsortkeys);
|
|
Assert(newclauses != NIL);
|
|
}
|
|
else
|
|
newclauses = mergeclauses;
|
|
}
|
|
try_mergejoin_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
innerpath,
|
|
merge_pathkeys,
|
|
newclauses,
|
|
NIL,
|
|
NIL,
|
|
jointype,
|
|
extra,
|
|
is_partial);
|
|
}
|
|
cheapest_startup_inner = innerpath;
|
|
}
|
|
|
|
/*
|
|
* Don't consider truncated sortkeys if we need all clauses.
|
|
*/
|
|
if (useallclauses)
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* match_unsorted_outer
|
|
* Creates possible join paths for processing a single join relation
|
|
* 'joinrel' by employing either iterative substitution or
|
|
* mergejoining on each of its possible outer paths (considering
|
|
* only outer paths that are already ordered well enough for merging).
|
|
*
|
|
* We always generate a nestloop path for each available outer path.
|
|
* In fact we may generate as many as five: one on the cheapest-total-cost
|
|
* inner path, one on the same with materialization, one on the
|
|
* cheapest-startup-cost inner path (if different), one on the
|
|
* cheapest-total inner-indexscan path (if any), and one on the
|
|
* cheapest-startup inner-indexscan path (if different).
|
|
*
|
|
* We also consider mergejoins if mergejoin clauses are available. See
|
|
* detailed comments in generate_mergejoin_paths.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'jointype' is the type of join to do
|
|
* 'extra' contains additional input values
|
|
*/
|
|
static void
|
|
match_unsorted_outer(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinType save_jointype = jointype;
|
|
bool nestjoinOK;
|
|
bool useallclauses;
|
|
Path *inner_cheapest_total = innerrel->cheapest_total_path;
|
|
Path *matpath = NULL;
|
|
ListCell *lc1;
|
|
|
|
/*
|
|
* Nestloop only supports inner, left, semi, and anti joins. Also, if we
|
|
* are doing a right or full mergejoin, we must use *all* the mergeclauses
|
|
* as join clauses, else we will not have a valid plan. (Although these
|
|
* two flags are currently inverses, keep them separate for clarity and
|
|
* possible future changes.)
|
|
*/
|
|
switch (jointype)
|
|
{
|
|
case JOIN_INNER:
|
|
case JOIN_LEFT:
|
|
case JOIN_SEMI:
|
|
case JOIN_ANTI:
|
|
nestjoinOK = true;
|
|
useallclauses = false;
|
|
break;
|
|
case JOIN_RIGHT:
|
|
case JOIN_FULL:
|
|
nestjoinOK = false;
|
|
useallclauses = true;
|
|
break;
|
|
case JOIN_UNIQUE_OUTER:
|
|
case JOIN_UNIQUE_INNER:
|
|
jointype = JOIN_INNER;
|
|
nestjoinOK = true;
|
|
useallclauses = false;
|
|
break;
|
|
default:
|
|
elog(ERROR, "unrecognized join type: %d",
|
|
(int) jointype);
|
|
nestjoinOK = false; /* keep compiler quiet */
|
|
useallclauses = false;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If inner_cheapest_total is parameterized by the outer rel, ignore it;
|
|
* we will consider it below as a member of cheapest_parameterized_paths,
|
|
* but the other possibilities considered in this routine aren't usable.
|
|
*/
|
|
if (PATH_PARAM_BY_REL(inner_cheapest_total, outerrel))
|
|
inner_cheapest_total = NULL;
|
|
|
|
/*
|
|
* If we need to unique-ify the inner path, we will consider only the
|
|
* cheapest-total inner.
|
|
*/
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
/* No way to do this with an inner path parameterized by outer rel */
|
|
if (inner_cheapest_total == NULL)
|
|
return;
|
|
inner_cheapest_total = (Path *)
|
|
create_unique_path(root, innerrel, inner_cheapest_total, extra->sjinfo);
|
|
Assert(inner_cheapest_total);
|
|
}
|
|
else if (nestjoinOK)
|
|
{
|
|
/*
|
|
* Consider materializing the cheapest inner path, unless
|
|
* enable_material is off or the path in question materializes its
|
|
* output anyway.
|
|
*/
|
|
if (enable_material && inner_cheapest_total != NULL &&
|
|
!ExecMaterializesOutput(inner_cheapest_total->pathtype))
|
|
matpath = (Path *)
|
|
create_material_path(innerrel, inner_cheapest_total);
|
|
}
|
|
|
|
foreach(lc1, outerrel->pathlist)
|
|
{
|
|
Path *outerpath = (Path *) lfirst(lc1);
|
|
List *merge_pathkeys;
|
|
|
|
/*
|
|
* We cannot use an outer path that is parameterized by the inner rel.
|
|
*/
|
|
if (PATH_PARAM_BY_REL(outerpath, innerrel))
|
|
continue;
|
|
|
|
/*
|
|
* If we need to unique-ify the outer path, it's pointless to consider
|
|
* any but the cheapest outer. (XXX we don't consider parameterized
|
|
* outers, nor inners, for unique-ified cases. Should we?)
|
|
*/
|
|
if (save_jointype == JOIN_UNIQUE_OUTER)
|
|
{
|
|
if (outerpath != outerrel->cheapest_total_path)
|
|
continue;
|
|
outerpath = (Path *) create_unique_path(root, outerrel,
|
|
outerpath, extra->sjinfo);
|
|
Assert(outerpath);
|
|
}
|
|
|
|
/*
|
|
* The result will have this sort order (even if it is implemented as
|
|
* a nestloop, and even if some of the mergeclauses are implemented by
|
|
* qpquals rather than as true mergeclauses):
|
|
*/
|
|
merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
|
|
outerpath->pathkeys);
|
|
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
/*
|
|
* Consider nestloop join, but only with the unique-ified cheapest
|
|
* inner path
|
|
*/
|
|
try_nestloop_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
inner_cheapest_total,
|
|
merge_pathkeys,
|
|
jointype,
|
|
extra);
|
|
}
|
|
else if (nestjoinOK)
|
|
{
|
|
/*
|
|
* Consider nestloop joins using this outer path and various
|
|
* available paths for the inner relation. We consider the
|
|
* cheapest-total paths for each available parameterization of the
|
|
* inner relation, including the unparameterized case.
|
|
*/
|
|
ListCell *lc2;
|
|
|
|
foreach(lc2, innerrel->cheapest_parameterized_paths)
|
|
{
|
|
Path *innerpath = (Path *) lfirst(lc2);
|
|
|
|
try_nestloop_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
innerpath,
|
|
merge_pathkeys,
|
|
jointype,
|
|
extra);
|
|
}
|
|
|
|
/* Also consider materialized form of the cheapest inner path */
|
|
if (matpath != NULL)
|
|
try_nestloop_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
matpath,
|
|
merge_pathkeys,
|
|
jointype,
|
|
extra);
|
|
}
|
|
|
|
/* Can't do anything else if outer path needs to be unique'd */
|
|
if (save_jointype == JOIN_UNIQUE_OUTER)
|
|
continue;
|
|
|
|
/* Can't do anything else if inner rel is parameterized by outer */
|
|
if (inner_cheapest_total == NULL)
|
|
continue;
|
|
|
|
/* Generate merge join paths */
|
|
generate_mergejoin_paths(root, joinrel, innerrel, outerpath,
|
|
save_jointype, extra, useallclauses,
|
|
inner_cheapest_total, merge_pathkeys,
|
|
false);
|
|
}
|
|
|
|
/*
|
|
* Consider partial nestloop and mergejoin plan if outerrel has any
|
|
* partial path and the joinrel is parallel-safe. However, we can't
|
|
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
|
|
* therefore we won't be able to properly guarantee uniqueness. Nor can
|
|
* we handle extra_lateral_rels, since partial paths must not be
|
|
* parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
|
|
* because they can produce false null extended rows.
|
|
*/
|
|
if (joinrel->consider_parallel &&
|
|
save_jointype != JOIN_UNIQUE_OUTER &&
|
|
save_jointype != JOIN_FULL &&
|
|
save_jointype != JOIN_RIGHT &&
|
|
outerrel->partial_pathlist != NIL &&
|
|
bms_is_empty(joinrel->lateral_relids))
|
|
{
|
|
if (nestjoinOK)
|
|
consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
|
|
save_jointype, extra);
|
|
|
|
/*
|
|
* If inner_cheapest_total is NULL or non parallel-safe then find the
|
|
* cheapest total parallel safe path. If doing JOIN_UNIQUE_INNER, we
|
|
* can't use any alternative inner path.
|
|
*/
|
|
if (inner_cheapest_total == NULL ||
|
|
!inner_cheapest_total->parallel_safe)
|
|
{
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
return;
|
|
|
|
inner_cheapest_total = get_cheapest_parallel_safe_total_inner(
|
|
innerrel->pathlist);
|
|
}
|
|
|
|
if (inner_cheapest_total)
|
|
consider_parallel_mergejoin(root, joinrel, outerrel, innerrel,
|
|
save_jointype, extra,
|
|
inner_cheapest_total);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* consider_parallel_mergejoin
|
|
* Try to build partial paths for a joinrel by joining a partial path
|
|
* for the outer relation to a complete path for the inner relation.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'jointype' is the type of join to do
|
|
* 'extra' contains additional input values
|
|
* 'inner_cheapest_total' cheapest total path for innerrel
|
|
*/
|
|
static void
|
|
consider_parallel_mergejoin(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra,
|
|
Path *inner_cheapest_total)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
/* generate merge join path for each partial outer path */
|
|
foreach(lc1, outerrel->partial_pathlist)
|
|
{
|
|
Path *outerpath = (Path *) lfirst(lc1);
|
|
List *merge_pathkeys;
|
|
|
|
/*
|
|
* Figure out what useful ordering any paths we create will have.
|
|
*/
|
|
merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
|
|
outerpath->pathkeys);
|
|
|
|
generate_mergejoin_paths(root, joinrel, innerrel, outerpath, jointype,
|
|
extra, false, inner_cheapest_total,
|
|
merge_pathkeys, true);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* consider_parallel_nestloop
|
|
* Try to build partial paths for a joinrel by joining a partial path for the
|
|
* outer relation to a complete path for the inner relation.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'jointype' is the type of join to do
|
|
* 'extra' contains additional input values
|
|
*/
|
|
static void
|
|
consider_parallel_nestloop(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinType save_jointype = jointype;
|
|
ListCell *lc1;
|
|
|
|
if (jointype == JOIN_UNIQUE_INNER)
|
|
jointype = JOIN_INNER;
|
|
|
|
foreach(lc1, outerrel->partial_pathlist)
|
|
{
|
|
Path *outerpath = (Path *) lfirst(lc1);
|
|
List *pathkeys;
|
|
ListCell *lc2;
|
|
|
|
/* Figure out what useful ordering any paths we create will have. */
|
|
pathkeys = build_join_pathkeys(root, joinrel, jointype,
|
|
outerpath->pathkeys);
|
|
|
|
/*
|
|
* Try the cheapest parameterized paths; only those which will produce
|
|
* an unparameterized path when joined to this outerrel will survive
|
|
* try_partial_nestloop_path. The cheapest unparameterized path is
|
|
* also in this list.
|
|
*/
|
|
foreach(lc2, innerrel->cheapest_parameterized_paths)
|
|
{
|
|
Path *innerpath = (Path *) lfirst(lc2);
|
|
|
|
/* Can't join to an inner path that is not parallel-safe */
|
|
if (!innerpath->parallel_safe)
|
|
continue;
|
|
|
|
/*
|
|
* If we're doing JOIN_UNIQUE_INNER, we can only use the inner's
|
|
* cheapest_total_path, and we have to unique-ify it. (We might
|
|
* be able to relax this to allow other safe, unparameterized
|
|
* inner paths, but right now create_unique_path is not on board
|
|
* with that.)
|
|
*/
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
if (innerpath != innerrel->cheapest_total_path)
|
|
continue;
|
|
innerpath = (Path *) create_unique_path(root, innerrel,
|
|
innerpath,
|
|
extra->sjinfo);
|
|
Assert(innerpath);
|
|
}
|
|
|
|
try_partial_nestloop_path(root, joinrel, outerpath, innerpath,
|
|
pathkeys, jointype, extra);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* hash_inner_and_outer
|
|
* Create hashjoin join paths by explicitly hashing both the outer and
|
|
* inner keys of each available hash clause.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'jointype' is the type of join to do
|
|
* 'extra' contains additional input values
|
|
*/
|
|
static void
|
|
hash_inner_and_outer(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
JoinType jointype,
|
|
JoinPathExtraData *extra)
|
|
{
|
|
JoinType save_jointype = jointype;
|
|
bool isouterjoin = IS_OUTER_JOIN(jointype);
|
|
List *hashclauses;
|
|
ListCell *l;
|
|
|
|
/*
|
|
* We need to build only one hashclauses list for any given pair of outer
|
|
* and inner relations; all of the hashable clauses will be used as keys.
|
|
*
|
|
* Scan the join's restrictinfo list to find hashjoinable clauses that are
|
|
* usable with this pair of sub-relations.
|
|
*/
|
|
hashclauses = NIL;
|
|
foreach(l, extra->restrictlist)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
|
|
|
|
/*
|
|
* If processing an outer join, only use its own join clauses for
|
|
* hashing. For inner joins we need not be so picky.
|
|
*/
|
|
if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
|
|
continue;
|
|
|
|
if (!restrictinfo->can_join ||
|
|
restrictinfo->hashjoinoperator == InvalidOid)
|
|
continue; /* not hashjoinable */
|
|
|
|
/*
|
|
* Check if clause has the form "outer op inner" or "inner op outer".
|
|
*/
|
|
if (!clause_sides_match_join(restrictinfo, outerrel, innerrel))
|
|
continue; /* no good for these input relations */
|
|
|
|
hashclauses = lappend(hashclauses, restrictinfo);
|
|
}
|
|
|
|
/* If we found any usable hashclauses, make paths */
|
|
if (hashclauses)
|
|
{
|
|
/*
|
|
* We consider both the cheapest-total-cost and cheapest-startup-cost
|
|
* outer paths. There's no need to consider any but the
|
|
* cheapest-total-cost inner path, however.
|
|
*/
|
|
Path *cheapest_startup_outer = outerrel->cheapest_startup_path;
|
|
Path *cheapest_total_outer = outerrel->cheapest_total_path;
|
|
Path *cheapest_total_inner = innerrel->cheapest_total_path;
|
|
|
|
/*
|
|
* If either cheapest-total path is parameterized by the other rel, we
|
|
* can't use a hashjoin. (There's no use looking for alternative
|
|
* input paths, since these should already be the least-parameterized
|
|
* available paths.)
|
|
*/
|
|
if (PATH_PARAM_BY_REL(cheapest_total_outer, innerrel) ||
|
|
PATH_PARAM_BY_REL(cheapest_total_inner, outerrel))
|
|
return;
|
|
|
|
/* Unique-ify if need be; we ignore parameterized possibilities */
|
|
if (jointype == JOIN_UNIQUE_OUTER)
|
|
{
|
|
cheapest_total_outer = (Path *)
|
|
create_unique_path(root, outerrel,
|
|
cheapest_total_outer, extra->sjinfo);
|
|
Assert(cheapest_total_outer);
|
|
jointype = JOIN_INNER;
|
|
try_hashjoin_path(root,
|
|
joinrel,
|
|
cheapest_total_outer,
|
|
cheapest_total_inner,
|
|
hashclauses,
|
|
jointype,
|
|
extra);
|
|
/* no possibility of cheap startup here */
|
|
}
|
|
else if (jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
cheapest_total_inner = (Path *)
|
|
create_unique_path(root, innerrel,
|
|
cheapest_total_inner, extra->sjinfo);
|
|
Assert(cheapest_total_inner);
|
|
jointype = JOIN_INNER;
|
|
try_hashjoin_path(root,
|
|
joinrel,
|
|
cheapest_total_outer,
|
|
cheapest_total_inner,
|
|
hashclauses,
|
|
jointype,
|
|
extra);
|
|
if (cheapest_startup_outer != NULL &&
|
|
cheapest_startup_outer != cheapest_total_outer)
|
|
try_hashjoin_path(root,
|
|
joinrel,
|
|
cheapest_startup_outer,
|
|
cheapest_total_inner,
|
|
hashclauses,
|
|
jointype,
|
|
extra);
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* For other jointypes, we consider the cheapest startup outer
|
|
* together with the cheapest total inner, and then consider
|
|
* pairings of cheapest-total paths including parameterized ones.
|
|
* There is no use in generating parameterized paths on the basis
|
|
* of possibly cheap startup cost, so this is sufficient.
|
|
*/
|
|
ListCell *lc1;
|
|
ListCell *lc2;
|
|
|
|
if (cheapest_startup_outer != NULL)
|
|
try_hashjoin_path(root,
|
|
joinrel,
|
|
cheapest_startup_outer,
|
|
cheapest_total_inner,
|
|
hashclauses,
|
|
jointype,
|
|
extra);
|
|
|
|
foreach(lc1, outerrel->cheapest_parameterized_paths)
|
|
{
|
|
Path *outerpath = (Path *) lfirst(lc1);
|
|
|
|
/*
|
|
* We cannot use an outer path that is parameterized by the
|
|
* inner rel.
|
|
*/
|
|
if (PATH_PARAM_BY_REL(outerpath, innerrel))
|
|
continue;
|
|
|
|
foreach(lc2, innerrel->cheapest_parameterized_paths)
|
|
{
|
|
Path *innerpath = (Path *) lfirst(lc2);
|
|
|
|
/*
|
|
* We cannot use an inner path that is parameterized by
|
|
* the outer rel, either.
|
|
*/
|
|
if (PATH_PARAM_BY_REL(innerpath, outerrel))
|
|
continue;
|
|
|
|
if (outerpath == cheapest_startup_outer &&
|
|
innerpath == cheapest_total_inner)
|
|
continue; /* already tried it */
|
|
|
|
try_hashjoin_path(root,
|
|
joinrel,
|
|
outerpath,
|
|
innerpath,
|
|
hashclauses,
|
|
jointype,
|
|
extra);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the joinrel is parallel-safe, we may be able to consider a
|
|
* partial hash join. However, we can't handle JOIN_UNIQUE_OUTER,
|
|
* because the outer path will be partial, and therefore we won't be
|
|
* able to properly guarantee uniqueness. Similarly, we can't handle
|
|
* JOIN_FULL and JOIN_RIGHT, because they can produce false null
|
|
* extended rows. Also, the resulting path must not be parameterized.
|
|
* We would be able to support JOIN_FULL and JOIN_RIGHT for Parallel
|
|
* Hash, since in that case we're back to a single hash table with a
|
|
* single set of match bits for each batch, but that will require
|
|
* figuring out a deadlock-free way to wait for the probe to finish.
|
|
*/
|
|
if (joinrel->consider_parallel &&
|
|
save_jointype != JOIN_UNIQUE_OUTER &&
|
|
save_jointype != JOIN_FULL &&
|
|
save_jointype != JOIN_RIGHT &&
|
|
outerrel->partial_pathlist != NIL &&
|
|
bms_is_empty(joinrel->lateral_relids))
|
|
{
|
|
Path *cheapest_partial_outer;
|
|
Path *cheapest_partial_inner = NULL;
|
|
Path *cheapest_safe_inner = NULL;
|
|
|
|
cheapest_partial_outer =
|
|
(Path *) linitial(outerrel->partial_pathlist);
|
|
|
|
/*
|
|
* Can we use a partial inner plan too, so that we can build a
|
|
* shared hash table in parallel? We can't handle
|
|
* JOIN_UNIQUE_INNER because we can't guarantee uniqueness.
|
|
*/
|
|
if (innerrel->partial_pathlist != NIL &&
|
|
save_jointype != JOIN_UNIQUE_INNER &&
|
|
enable_parallel_hash)
|
|
{
|
|
cheapest_partial_inner =
|
|
(Path *) linitial(innerrel->partial_pathlist);
|
|
try_partial_hashjoin_path(root, joinrel,
|
|
cheapest_partial_outer,
|
|
cheapest_partial_inner,
|
|
hashclauses, jointype, extra,
|
|
true /* parallel_hash */ );
|
|
}
|
|
|
|
/*
|
|
* Normally, given that the joinrel is parallel-safe, the cheapest
|
|
* total inner path will also be parallel-safe, but if not, we'll
|
|
* have to search for the cheapest safe, unparameterized inner
|
|
* path. If doing JOIN_UNIQUE_INNER, we can't use any alternative
|
|
* inner path.
|
|
*/
|
|
if (cheapest_total_inner->parallel_safe)
|
|
cheapest_safe_inner = cheapest_total_inner;
|
|
else if (save_jointype != JOIN_UNIQUE_INNER)
|
|
cheapest_safe_inner =
|
|
get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
|
|
|
|
if (cheapest_safe_inner != NULL)
|
|
try_partial_hashjoin_path(root, joinrel,
|
|
cheapest_partial_outer,
|
|
cheapest_safe_inner,
|
|
hashclauses, jointype, extra,
|
|
false /* parallel_hash */ );
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* select_mergejoin_clauses
|
|
* Select mergejoin clauses that are usable for a particular join.
|
|
* Returns a list of RestrictInfo nodes for those clauses.
|
|
*
|
|
* *mergejoin_allowed is normally set to true, but it is set to false if
|
|
* this is a right/full join and there are nonmergejoinable join clauses.
|
|
* The executor's mergejoin machinery cannot handle such cases, so we have
|
|
* to avoid generating a mergejoin plan. (Note that this flag does NOT
|
|
* consider whether there are actually any mergejoinable clauses. This is
|
|
* correct because in some cases we need to build a clauseless mergejoin.
|
|
* Simply returning NIL is therefore not enough to distinguish safe from
|
|
* unsafe cases.)
|
|
*
|
|
* We also mark each selected RestrictInfo to show which side is currently
|
|
* being considered as outer. These are transient markings that are only
|
|
* good for the duration of the current add_paths_to_joinrel() call!
|
|
*
|
|
* We examine each restrictinfo clause known for the join to see
|
|
* if it is mergejoinable and involves vars from the two sub-relations
|
|
* currently of interest.
|
|
*/
|
|
static List *
|
|
select_mergejoin_clauses(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
List *restrictlist,
|
|
JoinType jointype,
|
|
bool *mergejoin_allowed)
|
|
{
|
|
List *result_list = NIL;
|
|
bool isouterjoin = IS_OUTER_JOIN(jointype);
|
|
bool have_nonmergeable_joinclause = false;
|
|
ListCell *l;
|
|
|
|
foreach(l, restrictlist)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
|
|
|
|
/*
|
|
* If processing an outer join, only use its own join clauses in the
|
|
* merge. For inner joins we can use pushed-down clauses too. (Note:
|
|
* we don't set have_nonmergeable_joinclause here because pushed-down
|
|
* clauses will become otherquals not joinquals.)
|
|
*/
|
|
if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
|
|
continue;
|
|
|
|
/* Check that clause is a mergeable operator clause */
|
|
if (!restrictinfo->can_join ||
|
|
restrictinfo->mergeopfamilies == NIL)
|
|
{
|
|
/*
|
|
* The executor can handle extra joinquals that are constants, but
|
|
* not anything else, when doing right/full merge join. (The
|
|
* reason to support constants is so we can do FULL JOIN ON
|
|
* FALSE.)
|
|
*/
|
|
if (!restrictinfo->clause || !IsA(restrictinfo->clause, Const))
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* not mergejoinable */
|
|
}
|
|
|
|
/*
|
|
* Check if clause has the form "outer op inner" or "inner op outer".
|
|
*/
|
|
if (!clause_sides_match_join(restrictinfo, outerrel, innerrel))
|
|
{
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* no good for these input relations */
|
|
}
|
|
|
|
/*
|
|
* Insist that each side have a non-redundant eclass. This
|
|
* restriction is needed because various bits of the planner expect
|
|
* that each clause in a merge be associable with some pathkey in a
|
|
* canonical pathkey list, but redundant eclasses can't appear in
|
|
* canonical sort orderings. (XXX it might be worth relaxing this,
|
|
* but not enough time to address it for 8.3.)
|
|
*
|
|
* Note: it would be bad if this condition failed for an otherwise
|
|
* mergejoinable FULL JOIN clause, since that would result in
|
|
* undesirable planner failure. I believe that is not possible
|
|
* however; a variable involved in a full join could only appear in
|
|
* below_outer_join eclasses, which aren't considered redundant.
|
|
*
|
|
* This case *can* happen for left/right join clauses: the outer-side
|
|
* variable could be equated to a constant. Because we will propagate
|
|
* that constant across the join clause, the loss of ability to do a
|
|
* mergejoin is not really all that big a deal, and so it's not clear
|
|
* that improving this is important.
|
|
*/
|
|
update_mergeclause_eclasses(root, restrictinfo);
|
|
|
|
if (EC_MUST_BE_REDUNDANT(restrictinfo->left_ec) ||
|
|
EC_MUST_BE_REDUNDANT(restrictinfo->right_ec))
|
|
{
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* can't handle redundant eclasses */
|
|
}
|
|
|
|
result_list = lappend(result_list, restrictinfo);
|
|
}
|
|
|
|
/*
|
|
* Report whether mergejoin is allowed (see comment at top of function).
|
|
*/
|
|
switch (jointype)
|
|
{
|
|
case JOIN_RIGHT:
|
|
case JOIN_FULL:
|
|
*mergejoin_allowed = !have_nonmergeable_joinclause;
|
|
break;
|
|
default:
|
|
*mergejoin_allowed = true;
|
|
break;
|
|
}
|
|
|
|
return result_list;
|
|
}
|