Re: Pg_stat_replication shows sync standby with flush location behind primary in 9.1.5

On 4 October 2012 05:32, Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> wrote:
> I am seeing the situation where the reported flush location for the sync
> standby (standby1 below) is *behind* the reported current xlog location of
> the primary. This is Postgres 9.1.5 , and I was under the impression that
> transactions initiated on the master do not commit until the corresponding
> wal is flushed on the sync standby.
>
> Now the standby is definitely working in sync mode, because stopping it
> halts all write transactions on the primary (sync_standby_names contains
> only standby1). So is the reported lag in flush location merely an artifact
> of timing in the query, or is there something else going on? [1]

The writing of new WAL is independent of the wait that occurs on
commit, so it is entirely possible, even desirable, that the observed
effect occurs.

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Simon Riggs http://www.2ndQuadrant.com/
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