| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Greg Stark <gsstark(at)mit(dot)edu>, Mark Cave-Ayland <m(dot)cave-ayland(at)webbased(dot)co(dot)uk>, "'Manfred Koizar'" <mkoi-pg(at)aon(dot)at>, "'Bruce Momjian'" <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Cost of XLogInsert CRC calculations |
| Date: | 2005-06-01 02:36:29 |
| Message-ID: | 9291.1117593389@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Hmmm. I seem to recall asking myself why xl_prev existed if it wasn't
> used, but passed that by. Damn.
I couldn't believe it'd been overlooked this long, either. It's the
sort of thing that you assume got done the first time :-(
> PreAllocXLog was already a reason to have somebody prepare new xlog
> files ahead of them being used. Surely the right solution here is to
> have that agent prepare fresh/zeroed files prior to them being required.
Uh, why? That doubles the amount of physical I/O required to maintain
the WAL, and AFAICS it doesn't really add any safety that we can't get
in a more intelligent fashion.
regards, tom lane
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