Re: WAL & SHM principles

From: Martin Devera <devik(at)cdi(dot)cz>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: WAL & SHM principles
Date: 2001-03-08 08:55:09
Message-ID: Pine.LNX.4.10.10103080954070.30955-100000@luxik.cdi.cz
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> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > The only problem is that we would no longer have control over which
> > > pages made it to disk. The OS would perhaps write pages as we modified
> > > them. Not sure how important that is.
> >
> > Unfortunately, this alone is a *fatal* objection. See nearby
> > discussions about WAL behavior: we must be able to control the relative
> > timing of WAL write/flush and data page writes.
>
> Bummer.
>
BTW, what means "bummer" ?
But for many OSes you CAN control when to write data - you can mlock
individual pages.

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