Re: Is full_page_writes=off safe in conjunction with

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Martijn van Oosterhout <kleptog(at)svana(dot)org>
Cc: Hannu Krosing <hannu(at)skype(dot)net>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Is full_page_writes=off safe in conjunction with
Date: 2006-04-16 20:55:24
Message-ID: 18775.1145220924@sss.pgh.pa.us
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Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> I must be missing something obvious, but why don't we compress the
> xlogs? They appear to be quite compressable (>75%) with standard gzip...

Might be worth experimenting with, but I'm a bit dubious. We've seen
several tests showing that XLogInsert's calculation of a CRC for each
WAL record is a bottleneck (that's why we backed off from 64-bit CRC
to 32-bit recently). I'd think that any nontrivial compression
algorithm would be vastly slower than CRC ...

regards, tom lane

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