Re: [PATCH] A crash and subsequent recovery of the master can cause the slave to get out-of-sync

Your patch has been added to the PostgreSQL unapplied patches list at:
http://momjian.postgresql.org/cgi-bin/pgpatches

It will be applied as soon as one of the PostgreSQL committers reviews
and approves it.

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Florian G. Pflug wrote:
> Hi
> 
> I believe I have discovered the following problem in pgsql 8.2 and HEAD,
> concerning warm-standbys using WAL log shipping.
> 
> The problem is that after a crash, the master might complete incomplete
> actions via rm_cleanup() - but since it won't wal-log those changes,
> the slave won't know about this. This will at least prevent the creation
> of any further restart points on the slave (because safe_restartpoint)
> will never return true again - it it might even cause data corruption,
> if subsequent wal records are interpreted wrongly by the slave because
> it sees other data than the master did when it generated them.
> 
> Attached is a patch that lets RecoveryRestartPoint call all
> rm_cleanup() methods and create a restart point whenever it encounters
> a shutdown checkpoint in the wal (because those are generated after
> recovery). This ought not cause a performance degradation, because
> shutdown checkpoints will occur very infrequently.
> 
> The patch is per discussion with Simon Riggs.
> 
> I've not yet had a chance to test this patch, I only made sure
> that it compiles. I'm sending this out now because I hope this
> might make it into 8.2.4.
> 
> greetings, Florian Pflug


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