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Preparatory refactoring for parallel merge join support.

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Extract the logic used by hash_inner_and_outer into a separate
function, get_cheapest_parallel_safe_total_inner, so that it can
also be used to plan parallel merge joins.

Also, add a require_parallel_safe argument to the existing function
get_cheapest_path_for_pathkeys, because parallel merge join needs
to find the cheapest path for a given set of pathkeys that is
parallel-safe, not just the cheapest one overall.

Patch by me, reviewed by Dilip Kumar.

Discussion: http://postgr.es/m/CA+TgmoYOv+dFK0MWW6366dFj_xTnohQfoBDrHyB7d1oZhrgPjA@mail.gmail.com
This commit is contained in:
Robert Haas
2017-03-07 10:33:29 -05:00
parent 655393a022
commit a71f10189d
4 changed files with 43 additions and 22 deletions
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9
src/backend/optimizer/path/allpaths.c
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@ -1447,12 +1447,14 @@ generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
get_cheapest_path_for_pathkeys(childrel->pathlist,
pathkeys,
NULL,
STARTUP_COST);
STARTUP_COST,
false);
cheapest_total =
get_cheapest_path_for_pathkeys(childrel->pathlist,
pathkeys,
NULL,
TOTAL_COST);
TOTAL_COST,
false);
/*
* If we can't find any paths with the right order just use the
@ -1517,7 +1519,8 @@ get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
NIL,
required_outer,
TOTAL_COST);
TOTAL_COST,
false);
Assert(cheapest != NULL);
if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
return cheapest;