Re: We need to log aborted autovacuums

On Sat, Feb 5, 2011 at 12:54 PM, Cédric Villemain
<cedric(dot)villemain(dot)debian(at)gmail(dot)com> wrote:
> what do you implement exactly ?
> * The original request from Josh to get LOG when autovac can not run
> because of locks
> * VACOPT_NOWAIT, what is it ?

What the patch implements is:

If autovacuum can't get the table lock immediately, it skips the
table. This leaves the table still appearing to need autovacuuming,
so autovacuum will keep retrying (every 1 minute, or whatever you have
autovacuum_naptime set to) until it gets the lock. This seems clearly
better than the historical behavior of blocking on the lock, which can
potentially keep other tables in the database from getting vacuumed.

In the case where a table is skipped for this reason, we log a message
at log level LOG. The version of the patch I posted does that
unconditionally, but my intention was to change it before commit so
that it only logs the message if log_autovacuum_min_duration is
something other than -1.

Regular vacuum behaves as before - it waits for each table lock
individually. We could expose a NOWAIT option at the SQL level as
well, so that someone could do VACOPT (NOWAIT), if that's something
people want.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company