Re: lazy vacuum blocks analyze

Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
> My colleague hit interesting problem. His transaction hanged for a
> several days (PG8.3). We found that transaction (ANALYZE) command)
> waited on relation lock which had been acquired by lazy vacuum.
> Unfortunately, lazy vacuum on large table (38GB) takes veeeery long time
> - several days.

> The problem is that vacuum and analyze use same lock. If I understood
> correctly comment in analyze_rel() function it is not necessary.

> I think that it is very serious issue and dead space map does not help
> much in this case, because affected table is heavily modified.

> If there is not another problem I suggest to use two different locks for
> vacuum and analyze.

We would have to invent another lock type just for ANALYZE. It does not
seem worth it.

regards, tom lane