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Re: determining max_fsm_pages

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Patrick Hatcher <pathat(at)comcast(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: determining max_fsm_pages
Date: 2004-10-29 14:37:23
Message-ID: 15929.1099060643@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Patrick Hatcher <pathat(at)comcast(dot)net> writes:
> My question is this:  I have about 8 databases running on this server.  
> When I do a vacuum full on each of these databases, there is a INFO 
> section that I assume is the total pages used for that database.  Should 
> add ALL these individual pages together and pad the total and use this 
> as my new max_fsm_pages?  Should I do the same thing with max_fsm_relations?

No, the numbers shown at the end of a vacuum verbose printout reflect
the current cluster-wide FSM demand.  BTW you do *not* want to use FULL
because that's not going to reflect the FSM requirements when you are
just running normal vacuums.

I would vacuum all your databases (to make sure each one's FSM contents
are pretty up-to-date) and then take the numbers shown by the last one
as your targets.

If you find yourself having to raise max_fsm_relations, it may be
necessary to repeat the vacuuming cycle before you can get a decent
total for max_fsm_pages.  IIRC, the vacuum printout does include in
"needed" a count of pages that it would have stored if it'd had room;
but this is only tracked for relations that have an FSM relation entry.

			regards, tom lane

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