Re: Maintenance question / DB size anomaly...

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Kurt Overberg <kurt(at)hotdogrecords(dot)com>
Cc: Chris Browne <cbbrowne(at)acm(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Maintenance question / DB size anomaly...
Date: 2007-06-20 18:37:46
Message-ID: 28417.1182364666@sss.pgh.pa.us
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Kurt Overberg <kurt(at)hotdogrecords(dot)com> writes:
> Okay, so I did some digging with pg_filedump, and found the following:

> Block 406 ********************************************************
> Item 1 -- Length: 472 Offset: 7720 (0x1e28) Flags: USED
> XMIN: 1489323584 CMIN: 1 XMAX: 0 CMAX|XVAC: 0
> Block Id: 406 linp Index: 1 Attributes: 6 Size: 32
> infomask: 0x0912 (HASVARWIDTH|HASOID|XMIN_COMMITTED|XMAX_INVALID)

This is pretty much what you'd expect for a never-updated tuple...

> mydb=# select * from _my_cluster.sl_log_1 where ctid = '(406,1)';
> log_origin | log_xid | log_tableid | log_actionseq | log_cmdtype |
> log_cmddata
> ------------+---------+-------------+---------------+-------------
> +-------------
> (0 rows)

so I have to conclude that you've got a wraparound problem. What is the
current XID counter? (pg_controldata will give you that, along with a
lot of other junk.) It might also be interesting to take a look at
"ls -l $PGDATA/pg_clog"; the mod times on the files in there would give
us an idea how fast XIDs are being consumed.

regards, tom lane

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