From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Joachim Wieland <joe(at)mcknight(dot)de>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Logical decoding & exported base snapshot |
Date: | 2012-12-12 23:52:33 |
Message-ID: | 17860.1355356353@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2012-12-12 12:13:44 +0100, Andres Freund wrote:
>> This morning I wondered whether we couldn't protect against that by
>> acquiring share locks on the catalog rows pg_dump reads, that would
>> result in "could not serialize access due to concurrent update" type of
>> errors which would be easy enough discernible/translateable.
>> While pretty damn ugly that should take care of most of those issues,
>> shouldn't it?
How would it fix anything? The problem is with DDL that's committed and
gone before pg_dump ever gets to the table's pg_class row. Once it
does, and takes AccessShareLock on the relation, it's safe. Adding a
SELECT FOR SHARE step just adds more time before we can get that lock.
Also, locking the pg_class row doesn't provide protection against DDL
that doesn't modify the relation's pg_class row, of which there is
plenty.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Andres Freund | 2012-12-12 23:58:05 | Re: Logical decoding & exported base snapshot |
Previous Message | Andres Freund | 2012-12-12 23:45:16 | Re: Logical decoding & exported base snapshot |