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From: Oskari Saarenmaa <os@ohmu.fi>
To: Andres Freund <andres@2ndquadrant.com>
To: Peter Eisentraut <peter_e@gmx.net>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Jim Nasby <jim@nasby.net>
Cc: PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Subject: Re: REINDEX CONCURRENTLY 2.0
Date: Tue, 23 Dec 2014 10:54:39 +0200
Message-ID: <54992DCF.4040908@ohmu.fi> (raw)
In-Reply-To: <61E955E2-61D7-45E8-BC66-F021EA0CE3CE@2ndquadrant.com>
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13.11.2014, 23:50, Andres Freund kirjoitti:
> On November 13, 2014 10:23:41 PM CET, Peter Eisentraut <peter_e@gmx.net> wrote:
>> On 11/12/14 7:31 PM, Andres Freund wrote:
>>> Yes, it sucks. But it beats not being able to reindex a relation with
>> a
>>> primary key (referenced by a fkey) without waiting several hours by a
>>> couple magnitudes. And that's the current situation.
>>
>> That's fine, but we have, for better or worse, defined CONCURRENTLY :=
>> does not take exclusive locks.  Use a different adverb for an
>> in-between
>> facility.
> 
> I think that's not actually a service to our users. They'll have to adapt their scripts and knowledge when we get around to the more concurrent version. What exactly CONCURRENTLY means is already not strictly defined and differs between the actions.
> 
> I'll note that DROP INDEX CONCURRENTLY actually already  internally acquires an AEL lock. Although it's a bit harder to see the consequences of that.

If the short-lived lock is the only blocker for this feature at the
moment could we just require an additional qualifier for CONCURRENTLY
(FORCE?) until the lock can be removed, something like:

tmp# REINDEX INDEX CONCURRENTLY tmp_pkey;
ERROR:  REINDEX INDEX CONCURRENTLY is not fully concurrent; use REINDEX
INDEX CONCURRENTLY FORCE to perform reindex with a short-lived lock.

tmp=# REINDEX INDEX CONCURRENTLY FORCE tmp_pkey;
REINDEX

It's not optimal, but currently there's no way to reindex a primary key
anywhere close to concurrently and a short lock would be a huge
improvement over the current situation.

/ Oskari



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