Re: [HACKERS] wal_checksum = on (default) | off

From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-hackers(at)postgresql(dot)org>, <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] wal_checksum = on (default) | off
Date: 2007-01-05 10:01:31
Message-ID: E1539E0ED7043848906A8FF995BDA57901A35888@m0143.s-mxs.net
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> > >>> Recovery can occur with/without same setting of wal_checksum, to
avoid
> > >>> complications from crashes immediately after turning GUC on.
> > >>
> > >> Surely not. Otherwise even the "on" setting is not really a
defense.
> >
> > > Only when the CRC is exactly zero, which happens very very rarely.
> >
> > "It works most of the time" doesn't exactly satisfy me. What's the

Agreed

> > use-case for changing the variable on the fly anyway? Seems a
better
> > solution is just to lock down the setting at postmaster start.

I guess that the use case is more for a WAL based replicate, that
has/wants a different setting. Maybe we want a WAL entry for the change,
or force a log switch (so you can interrupt the replicate, change it's
setting
and proceed with the next log) ?

Maybe a 3rd mode for replicates that ignores 0 CRC's ?

Andreas

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