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Commit41e2b84

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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 itssubroutines for JOIN_UNIQUE_INNER cases (it should pass JOIN_INNER), and itthought that it could pass paths other than innerrel->cheapest_total_pathto create_unique_path, which create_unique_path is not on board with.These bugs would lead to assertion failures or other errors, suggestingthat this code path hasn't been tested much.hash_inner_and_outer's code for parallel join effectively treated bothJOIN_UNIQUE_OUTER and JOIN_UNIQUE_INNER the same as JOIN_INNER (fordifferent reasons :-(), leading to incorrect plans that treated a semijoinas if it were a plain join.Michael Day submitted a test case demonstrating that hash_inner_and_outerfailed for JOIN_UNIQUE_OUTER, and I found the other cases through codereview.Report:https://postgr.es/m/D0E8A029-D1AC-42E8-979A-5DE4A77E4413@rcmail.com
1 parentca5f885 commit41e2b84

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‎src/backend/optimizer/path/joinpath.c

Lines changed: 20 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1217,8 +1217,12 @@ consider_parallel_nestloop(PlannerInfo *root,
12171217
JoinTypejointype,
12181218
JoinPathExtraData*extra)
12191219
{
1220+
JoinTypesave_jointype=jointype;
12201221
ListCell*lc1;
12211222

1223+
if (jointype==JOIN_UNIQUE_INNER)
1224+
jointype=JOIN_INNER;
1225+
12221226
foreach(lc1,outerrel->partial_pathlist)
12231227
{
12241228
Path*outerpath= (Path*)lfirst(lc1);
@@ -1244,18 +1248,19 @@ consider_parallel_nestloop(PlannerInfo *root,
12441248
continue;
12451249

12461250
/*
1247-
*Like match_unsorted_outer, we onlyconsider a single nestloop
1248-
*path when the jointype is JOIN_UNIQUE_INNER.But we have to
1249-
*scan cheapest_parameterized_paths tofind the one we want to
1250-
*consider, because cheapest_total_path mightnotbe
1251-
*parallel-safe.
1251+
*If we're doing JOIN_UNIQUE_INNER, wecanonlyuse the inner's
1252+
*cheapest_total_path, and we have to unique-ify it.(We might
1253+
*be able torelax this to allow other safe, unparameterized
1254+
*inner paths, but right now create_unique_path isnoton board
1255+
*with that.)
12521256
*/
1253-
if (jointype==JOIN_UNIQUE_INNER)
1257+
if (save_jointype==JOIN_UNIQUE_INNER)
12541258
{
1255-
if (!bms_is_empty(PATH_REQ_OUTER(innerpath)))
1259+
if (innerpath!=innerrel->cheapest_total_path)
12561260
continue;
12571261
innerpath= (Path*)create_unique_path(root,innerrel,
1258-
innerpath,extra->sjinfo);
1262+
innerpath,
1263+
extra->sjinfo);
12591264
Assert(innerpath);
12601265
}
12611266

@@ -1284,6 +1289,7 @@ hash_inner_and_outer(PlannerInfo *root,
12841289
JoinTypejointype,
12851290
JoinPathExtraData*extra)
12861291
{
1292+
JoinTypesave_jointype=jointype;
12871293
boolisouterjoin=IS_OUTER_JOIN(jointype);
12881294
List*hashclauses;
12891295
ListCell*l;
@@ -1450,9 +1456,9 @@ hash_inner_and_outer(PlannerInfo *root,
14501456
* extended rows. Also, the resulting path must not be parameterized.
14511457
*/
14521458
if (joinrel->consider_parallel&&
1453-
jointype!=JOIN_UNIQUE_OUTER&&
1454-
jointype!=JOIN_FULL&&
1455-
jointype!=JOIN_RIGHT&&
1459+
save_jointype!=JOIN_UNIQUE_OUTER&&
1460+
save_jointype!=JOIN_FULL&&
1461+
save_jointype!=JOIN_RIGHT&&
14561462
outerrel->partial_pathlist!=NIL&&
14571463
bms_is_empty(joinrel->lateral_relids))
14581464
{
@@ -1466,11 +1472,12 @@ hash_inner_and_outer(PlannerInfo *root,
14661472
* Normally, given that the joinrel is parallel-safe, the cheapest
14671473
* total inner path will also be parallel-safe, but if not, we'll
14681474
* have to search cheapest_parameterized_paths for the cheapest
1469-
* unparameterized inner path.
1475+
* safe, unparameterized inner path. If doing JOIN_UNIQUE_INNER,
1476+
* we can't use any alternative inner path.
14701477
*/
14711478
if (cheapest_total_inner->parallel_safe)
14721479
cheapest_safe_inner=cheapest_total_inner;
1473-
else
1480+
elseif (save_jointype!=JOIN_UNIQUE_INNER)
14741481
{
14751482
ListCell*lc;
14761483

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