From: Alvaro Herrera <alvherre@commandprompt.com>
To: George Pavlov <gpavlov@mynewplace.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: stats reset during pg_restore?
Date: Sun, 27 Aug 2006 10:37:54 -0400
Message-ID: <20060827143754.GA13665@alvh.no-ip.org> (raw)
In-Reply-To: <8C5B026B51B6854CBE88121DBF097A863CD6DC@ehost010-33.exch010.intermedia.net>
References: <20060827024554.GD30132@alvh.no-ip.org>
<8C5B026B51B6854CBE88121DBF097A863CD6DC@ehost010-33.exch010.intermedia.net>
George Pavlov wrote:
> Based on how it works it seems that a server crash might lose the
> in-memory stats data as well?
Yeah, IIRC the postmaster removes the stat file after crash recovery.
It doesn't check the file for correctness.
> I imagine PITR does not take care of that special file (where is it
> by, by the way?). I have not worked with replication (yet), but I
> imagine replica databases will also be agnostic of the master's stats?
Neither PITR nor the replication systems I know about do anything about
the stats.
The file is $PGDATA/global/pgstat.stat
The code to read it, which is at the same time the documentation to its
format, is in src/backend/postmaster/pgstat.c, function
pgstat_read_statfile. It's quite simple. I think you could read it in
Perl if you wanted; and rewrite the file again after a restore (you'd
need to change the Oids in the table entries, etc).
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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To: pgsql-performance@postgresql.org
Cc: alvherre@commandprompt.com, gpavlov@mynewplace.com
Subject: Re: stats reset during pg_restore?
In-Reply-To: <20060827143754.GA13665@alvh.no-ip.org>
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