From: | Greg Stark <stark(at)mit(dot)edu> |
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To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Robert Haas <robertmhaas(at)gmail(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Logical replication in the same cluster |
Date: | 2017-05-01 21:20:47 |
Message-ID: | CAM-w4HP5jRP9sr=XVk0Ckpdyz6nDe3x5s2iXus-6AAZ8Ke-7tA@mail.gmail.com |
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On 1 May 2017 at 19:24, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> There is no inherent reason why the CREATE INDEX CONCURRENTLY style of
>> using multiple transactions makes it necessary to leave a mess behind
>> in the event of an error or hard crash. Is someone going to get around
>> to fixing the problem for CREATE INDEX CONCURRENTLY (e.g., having
>> extra steps to drop the useless index during recovery)? IIRC, this was
>> always the plan.
>
> Doing catalog changes in recovery is frought with problems. Essentially
> requires starting one worker per database, before allowing access.
The "plan" was to add more layers PG_TRY and transactions so that if
there was an error during building the index all the remnants of the
failed index build got cleaned up. But when I went tried to actually
do it the problem seemed to metastatize and it was going to require
two or three layers of messy nested PG_TRY and extra transactions.
Perhaps there's a cleaner way to structure it and I should look again.
I don't recall ever having a plan to do anything in recovery. I think
we did talk about why it was hard to mark hash indexes invalid during
recovery which was probably the same problem.
--
greg
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