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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
View File

@ -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;

23
src/backend/optimizer/path/joinpath.c
View File

@ -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,

29
src/backend/optimizer/path/pathkeys.c
View File

@ -337,11 +337,13 @@ pathkeys_contained_in(List *keys1, List *keys2)
* 'pathkeys' represents a required ordering (in canonical form!)
* 'required_outer' denotes allowable outer relations for parameterized paths
* 'cost_criterion' is STARTUP_COST or TOTAL_COST
* 'require_parallel_safe' causes us to consider only parallel-safe paths
*/
Path *
get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
Relids required_outer,
CostSelector cost_criterion)
CostSelector cost_criterion,
bool require_parallel_safe)
{
Path *matched_path = NULL;
ListCell *l;
@ -358,6 +360,9 @@ get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
compare_path_costs(matched_path, path, cost_criterion) <= 0)
continue;
if (require_parallel_safe && !path->parallel_safe)
continue;
if (pathkeys_contained_in(pathkeys, path->pathkeys) &&
bms_is_subset(PATH_REQ_OUTER(path), required_outer))
matched_path = path;
@ -407,6 +412,28 @@ get_cheapest_fractional_path_for_pathkeys(List *paths,
return matched_path;
}
/*
* get_cheapest_parallel_safe_total_inner
* Find the unparameterized parallel-safe path with the least total cost.
*/
Path *
get_cheapest_parallel_safe_total_inner(List *paths)
{
ListCell *l;
foreach(l, paths)
{
Path *innerpath = (Path *) lfirst(l);
if (innerpath->parallel_safe &&
bms_is_empty(PATH_REQ_OUTER(innerpath)))
return innerpath;
}
return NULL;
}
/****************************************************************************
* NEW PATHKEY FORMATION
****************************************************************************/