Re: BUG #15350: Getting invalid cache ID: 11 Errors

On Tue, Aug 28, 2018 at 2:40 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Thomas Munro <thomas.munro@enterprisedb.com> writes:
> > We could probably improve that situation by making syscache lookups
> > (and probably other things too) fail when called from _PG_init() in
> > regular backends so that extension authors are made aware of this
> > hazard, or perhaps go the other way and change the order we do things
> > in parallel workers.
>
> Hmm.  There's an argument to be made for the latter: we don't really
> want stuff failing in parallel workers if it works fine normally.
>
> On the other hand, it seems clear to me that we *don't* want extensions to
> be doing stuff like syscache lookups in _PG_init(), because that would
> prevent them from working as shared_preload_libraries entries.
>
> And on the third hand, intentionally breaking code that used to work
> isn't likely to win us many friends either.  So I'm not sure that your
> first option is really tenable.  Perhaps we could get away with doing
> it in HEAD and not back-patching ... but that does little for existing
> problems.

Ok, so I guess we should just  make it work then.  Here's throw-away
test patch to make "unaccent" blow up in this way, and a draft patch
to reorder things so that it works.

CREATE EXTENSION unaccent;
CREATE TABLE t AS SELECT 'hello world' AS v FROM generate_series(1, 1000000);
ANALYZE t;
EXPLAIN ANALYZE SELECT COUNT(unaccent(v)) FROM t;

-- 
Thomas Munro
http://www.enterprisedb.com