[Pgcluster-general] technical question

[Andreas Kostyrka]

* a.mitani at sra-europe.com <a.mitani at sra-europe.com> [070124 14:56]:
> Hi,
> 
> PGCluster is using a "query based relication".
> And all data writing query is set queue in replication server.
> Each replicated query execute from this queue one by one.
> 
> Transaction isolation is controled in each Cluster DB it self.
> It's a simple, isn't it :)

Not, because with READ COMMITED isolation level, the data that a
subselect returns is strictly depending upon the timing of concurrent
transactions. This means the statement below is not deterministic not
just because of the now, but also because of the simple subselect.

Without the subquery, e.g. when the app featches the data and inserts
it into a new query, that's not a problem for the replication, because
the app chooses what is the right value. 

Andreas