From a99922f966f57fcccee3b6e02a9df62789493dbc Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 12 Jan 2018 15:46:37 -0500 Subject: Avoid unnecessary failure in SELECT concurrent with ALTER NO INHERIT. If a query against an inheritance tree runs concurrently with an ALTER TABLE that's disinheriting one of the tree members, it's possible to get a "could not find inherited attribute" error because after obtaining lock on the removed member, make_inh_translation_list sees that its columns have attinhcount=0 and decides they aren't the columns it's looking for. An ideal fix, perhaps, would avoid including such a just-removed member table in the query at all; but there seems no way to accomplish that without adding expensive catalog rechecks or creating a likelihood of deadlocks. Instead, let's just drop the check on attinhcount. In this way, a query that's included a just-disinherited child will still succeed, which is not a completely unreasonable behavior. This problem has existed for a long time, so back-patch to all supported branches. Also add an isolation test verifying related behaviors. Patch by me; the new isolation test is based on Kyotaro Horiguchi's work. Discussion: https://postgr.es/m/20170626.174612.23936762.horiguchi.kyotaro@lab.ntt.co.jp --- src/backend/optimizer/prep/prepunion.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'src/backend/optimizer/prep/prepunion.c') diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c index e80ad7753de..0c2bb5d51f3 100644 --- a/src/backend/optimizer/prep/prepunion.c +++ b/src/backend/optimizer/prep/prepunion.c @@ -1498,7 +1498,7 @@ make_inh_translation_list(Relation oldrelation, Relation newrelation, */ if (old_attno < newnatts && (att = new_tupdesc->attrs[old_attno]) != NULL && - !att->attisdropped && att->attinhcount != 0 && + !att->attisdropped && strcmp(attname, NameStr(att->attname)) == 0) new_attno = old_attno; else @@ -1506,7 +1506,7 @@ make_inh_translation_list(Relation oldrelation, Relation newrelation, for (new_attno = 0; new_attno < newnatts; new_attno++) { att = new_tupdesc->attrs[new_attno]; - if (!att->attisdropped && att->attinhcount != 0 && + if (!att->attisdropped && strcmp(attname, NameStr(att->attname)) == 0) break; } -- cgit v1.2.3