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Fix bogus handling of JOIN_UNIQUE_OUTER/INNER cases for parallel joins. 

consider_parallel_nestloop passed the wrong jointype down to its
subroutines for JOIN_UNIQUE_INNER cases (it should pass JOIN_INNER), and it
thought that it could pass paths other than innerrel->cheapest_total_path
to create_unique_path, which create_unique_path is not on board with.
These bugs would lead to assertion failures or other errors, suggesting
that this code path hasn't been tested much.

hash_inner_and_outer's code for parallel join effectively treated both
JOIN_UNIQUE_OUTER and JOIN_UNIQUE_INNER the same as JOIN_INNER (for
different reasons :-(), leading to incorrect plans that treated a semijoin
as if it were a plain join.

Michael Day submitted a test case demonstrating that hash_inner_and_outer
failed for JOIN_UNIQUE_OUTER, and I found the other cases through code
review.

Report: https://postgr.es/m/D0E8A029-D1AC-42E8-979A-5DE4A77E4413@rcmail.com
This commit is contained in:
Tom Lane 2016-11-29 19:32:35 -05:00
parent ca5f885020
commit 41e2b84ce1
1 changed files with 20 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/backend/optimizer/path/joinpath.c
View File

@ -1217,8 +1217,12 @@ consider_parallel_nestloop(PlannerInfo *root,
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);
@ -1244,18 +1248,19 @@ consider_parallel_nestloop(PlannerInfo *root,
continue;
/*
* Like match_unsorted_outer, we only consider a single nestloop
* path when the jointype is JOIN_UNIQUE_INNER. But we have to
* scan cheapest_parameterized_paths to find the one we want to
* consider, because cheapest_total_path might not be
* parallel-safe.
* 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 (jointype == JOIN_UNIQUE_INNER)
if (save_jointype == JOIN_UNIQUE_INNER)
{
if (!bms_is_empty(PATH_REQ_OUTER(innerpath)))
if (innerpath != innerrel->cheapest_total_path)
continue;
innerpath = (Path *) create_unique_path(root, innerrel,
innerpath, extra->sjinfo);
innerpath,
extra->sjinfo);
Assert(innerpath);
}
@ -1284,6 +1289,7 @@ hash_inner_and_outer(PlannerInfo *root,
JoinType jointype,
JoinPathExtraData *extra)
{
JoinType save_jointype = jointype;
bool isouterjoin = IS_OUTER_JOIN(jointype);
List *hashclauses;
ListCell *l;
@ -1450,9 +1456,9 @@ hash_inner_and_outer(PlannerInfo *root,
* extended rows. Also, the resulting path must not be parameterized.
*/
if (joinrel->consider_parallel &&
jointype != JOIN_UNIQUE_OUTER &&
jointype != JOIN_FULL &&
jointype != JOIN_RIGHT &&
save_jointype != JOIN_UNIQUE_OUTER &&
save_jointype != JOIN_FULL &&
save_jointype != JOIN_RIGHT &&
outerrel->partial_pathlist != NIL &&
bms_is_empty(joinrel->lateral_relids))
{
@ -1466,11 +1472,12 @@ hash_inner_and_outer(PlannerInfo *root,
* 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 cheapest_parameterized_paths for the cheapest
* unparameterized inner path.
* 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
else if (save_jointype != JOIN_UNIQUE_INNER)
{
ListCell *lc;