Re: how to avoid deadlock on masive update with multiples delete - Mailing list pgsql-performance

Merlin Moncure <mmoncure@gmail.com> writes:
> Can't it be forced like this (assuming it is in fact a vanilla order
> by problem)?

> EXPLAIN DELETE FROM test USING (SELECT g FROM test ORDER BY
> ctid FOR UPDATE) x where x.g = test.g;

> (emphasis on 'for update')

Hm ... yeah, that might work, once you redefine the problem as "get the
row locks in a consistent order" rather than "do the updates in a
consistent order".  But I'd be inclined to phrase it as

EXPLAIN DELETE FROM test USING (SELECT ctid FROM test ORDER BY
g FOR UPDATE) x where x.ctid = test.ctid;

I'm not sure that "ORDER BY ctid" is really very meaningful here; think
about FOR UPDATE switching its attention to updated versions of rows.

            regards, tom lane