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From: David Rowley <david.rowley@2ndquadrant.com>
Date: Thu, 14 Jun 2018 21:49:58 +1200
Message-ID: 
 <CAKJS1f-XFWJdnpywUqOrd0_OmbM9FJsOYz+=y_0R_7CCPFNFVw@mail.gmail.com>
Subject: Re: why partition pruning doesn't work?
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>,
	Dmitry Dolgov <9erthalion6@gmail.com>, Jeff Janes <jeff.janes@gmail.com>,
	Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>,
 Pavel Stehule <pavel.stehule@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On 14 June 2018 at 04:10, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> There's still one thing I'm a bit confused about here.  I noticed that
> we weren't actually using the partopfamily and partopcintype fields in
> PartitionPruneContext, so I removed them.  But that still leaves both
> partsupfunc and partcollation as pointers into the relcache that were
> subject to this hazard.  My testing agrees with lousyjack's results
> that both of those were, in fact, being improperly accessed.  The OID
> comparison effect I mentioned upthread explains why the buildfarm's
> cache-clobbering members failed to notice any problem with garbage
> partsupfunc data ... but why did we not see any complaints about invalid
> collation OIDs?  Tis strange.

FWIW It's not working for me before e23bae82cf3 with
CLOBBER_FREED_MEMORY, CLOBBER_CACHE_ALWAYS and RELCACHE_FORCE_RELEASE,
and:

create table listp (a text) partition by list(a);
create table listp1 partition of listp for values in ('1');
select * from listp where a = (select '1');

I get:

ERROR:  cache lookup failed for collation 2139062143

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