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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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23
src/backend/optimizer/path/joinpath.c
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@ -936,7 +936,8 @@ generate_mergejoin_paths(PlannerInfo *root,
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
trialsortkeys,
NULL,
TOTAL_COST);
TOTAL_COST,
false);
if (innerpath != NULL &&
(cheapest_total_inner == NULL ||
compare_path_costs(innerpath, cheapest_total_inner,
@ -971,7 +972,8 @@ generate_mergejoin_paths(PlannerInfo *root,
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
trialsortkeys,
NULL,
STARTUP_COST);
STARTUP_COST,
false);
if (innerpath != NULL &&
(cheapest_startup_inner == NULL ||
compare_path_costs(innerpath, cheapest_startup_inner,
@ -1517,21 +1519,8 @@ hash_inner_and_outer(PlannerInfo *root,
if (cheapest_total_inner->parallel_safe)
cheapest_safe_inner = cheapest_total_inner;
else if (save_jointype != JOIN_UNIQUE_INNER)
{
ListCell *lc;
foreach(lc, innerrel->pathlist)
{
Path *innerpath = (Path *) lfirst(lc);
if (innerpath->parallel_safe &&
bms_is_empty(PATH_REQ_OUTER(innerpath)))
{
cheapest_safe_inner = innerpath;
break;
}
}
}
cheapest_safe_inner =
get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
if (cheapest_safe_inner != NULL)
try_partial_hashjoin_path(root, joinrel,