Horton

Re: [HACKERS] Full page writes improvement, code update

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Koichi Suzuki <suzuki.koichi@oss.ntt.co.jp>
Cc: Simon Riggs <simon@2ndquadrant.com>, josh@agliodbs.com, pgsql-hackers@postgresql.org, pgsql-patches@postgresql.org
Date: 2007-04-11T22:48:23Z
Lists: pgsql-hackers 
Koichi Suzuki <suzuki.koichi@oss.ntt.co.jp> writes:
> For more information, when checkpoint interval is one hour, the amount
> of the archived log size was as follows:
> cp:             3.1GB
> gzip:           1.5GB
> pg_compresslog: 0.3GB

The notion that 90% of the WAL could be backup blocks even at very long
checkpoint intervals struck me as excessive, so I went looking for a
reason, and I may have found one.  There has been a bug in CVS HEAD
since Feb 8 causing every btree page split record to include a backup
block whether needed or not.  If these numbers were taken with recent
8.3 code, please retest with current HEAD.

			regards, tom lane