Hannu Krosing wrote: > Ühel kenal päeval, P, 2006-07-30 kell 14:11, kirjutas Alvaro Herrera:
> > What was idea behind moving vac_update_relstats to a separate > > transaction? I'm wondering if it's still needed, if it further enhances > > the system somehow, or your patch did something differently than what > > was applied. > > The part of transactions which actually modified the data (iirc it updates > relpages and reltuples in pg_class) is not safe to ignore by concurrent > vacuum, say a vacuum on pg_class . > > When the updating is done in the same trx that marks itself inVacuum, > then these vacuums would be permitted to remove the old versions of > pg_class and then, in case the inVacuum transaction aborts after that we > are left with no valid pg_class row. I understand. But the pg_class row is updated using in-place update, which means that it continues having the same Xmin as before -- to the rest of the system, it's exactly the same row as before, and it won't be removed. So this is not a problem. Thanks for clarifying. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
