From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | pgsql-committers(at)postgresql(dot)org |
Subject: | pgsql: Avoid unnecessary failure in SELECT concurrent with ALTER NO INH |
Date: | 2018-01-12 20:47:15 |
Message-ID: | E1ea6EN-0005Dr-U8@gemulon.postgresql.org |
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Lists: | pgsql-committers |
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
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/680d540502609b422d378a1b8e0c10cac3c60084
Modified Files
--------------
src/backend/optimizer/prep/prepunion.c | 4 +-
src/test/isolation/expected/alter-table-4.out | 57 +++++++++++++++++++++++++++
src/test/isolation/isolation_schedule | 1 +
src/test/isolation/specs/alter-table-4.spec | 37 +++++++++++++++++
4 files changed, 97 insertions(+), 2 deletions(-)
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