Re: BUG #11457: The below query crashes 9.3.5, but not 9.3.4

Nelson Page wrote:
> As mentioned in the original title, we cannot reproduce this crash in 9.3.4, but can in 9.3.5. So our particular crash does not go back to 9.1 (unless the 9.1 you mention is some other context maybe?)

Bug fixes are backpatched to supported branches; 9.3.4 is older than
9.1.14. 9.1.14 does contain the backpatched bug fix which seems to have
introduced the new bug:

commit 555d0b2000e33fd1ad2721015996a66c43bbb3cd
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Date: Thu Jun 26 10:41:10 2014 -0700

Back-patch "Fix EquivalenceClass processing for nested append relations".

When we committed a87c729153e372f3731689a7be007bc2b53f1410, we somehow
failed to notice that it didn't merely improve plan quality for expression
indexes; there were very closely related cases that failed outright with
"could not find pathkey item to sort". The failing cases seem to be those
where the planner was already capable of selecting a MergeAppend plan,
and there was inheritance involved: the lack of appropriate eclass child
members would prevent prepare_sort_from_pathkeys() from succeeding on the
MergeAppend's child plan nodes for inheritance child tables.

Accordingly, back-patch into 9.1 through 9.3, along with an extra
regression test case covering the problem.

Per trouble report from Michael Glaesemann.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services