From: Andres Freund <andres@anarazel.de>
To: Craig Ringer <craig@2ndquadrant.com>
Cc: obartunov@gmail.com, Bruce Momjian <bruce@momjian.us>
Cc: Joshua D. Drake <jd@commandprompt.com>
Cc: Petr Jelinek <petr@2ndquadrant.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: pglogical - logical replication contrib module
Date: Wed, 17 Feb 2016 09:27:50 +0100
Message-ID: <20160217082749.GI25464@awork2.anarazel.de> (raw)
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On 2016-02-17 09:33:56 +0800, Craig Ringer wrote:
> Some DDL operations don't translate well to a series of replicatable
> actions. The case I hit the most is
>
> ALTER TABLE mytable ADD COLUMN somecolumn sometype NOT NULL DEFAULT
> some_function();
>
> This is executed (simplified) by taking an ACCESS EXCLUSIVE lock, changing
> the catalogs but not making the changes visible yet, rewriting the table,
> and committing to make the rewritten table and the catalog changes visible.
>
> That won't work well with logical replication.
FWIW, I think this is much less a fundamental, and more an
implementation issue. Falling back to just re-replicating the table, and
then optimizing a few common cases (only immutable DEFALUT/USING
involved) should be enough for a while.
Lets get the basics right, before reaching for the moon.
Greetings,
Andres Freund
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Cc: andres@anarazel.de, craig@2ndquadrant.com, bruce@momjian.us, jd@commandprompt.com, petr@2ndquadrant.com
Subject: Re: pglogical - logical replication contrib module
In-Reply-To: <20160217082749.GI25464@awork2.anarazel.de>
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