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Re: autovacuum stress-testing our system

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Euler Taveira <euler(at)timbira(dot)com>
Cc: Tomas Vondra <tv(at)fuzzy(dot)cz>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: autovacuum stress-testing our system
Date: 2012-09-26 15:27:44
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Lists: pgsql-hackers
Excerpts from Euler Taveira's message of mié sep 26 11:53:27 -0300 2012:
> On 26-09-2012 09:43, Tomas Vondra wrote:

> > 5) splitting the single stat file into multiple pieces - e.g. per database,
> >    written separately, so that the autovacuum workers don't need to read all
> >    the data even for databases that don't need to be vacuumed. This might be
> >    combined with (4).
> > 
> IMHO that's the definitive solution. It would be one file per database plus a
> global one. That way, the check would only read the global.stat and process
> those database that were modified. Also, an in-memory map could store that
> information to speed up the checks.


> The only downside I can see is that you
> will increase the number of opened file descriptors.

Note that most users of pgstat will only have two files open (instead of
one as currently) -- one for shared, one for their own database.  Only
pgstat itself and autovac launcher would need to open pgstat files for
all databases; but both do not have a need to open other files
(arbitrary tables) so this shouldn't be a major problem.

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Training & Services

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