Re: is sync rep stalled?

Heikki Linnakangas wrote:
> On 04.10.2010 10:49, Markus Wanner wrote:
> > On 10/04/2010 09:18 AM, Heikki Linnakangas wrote:
> >> With 'replay' and hot standby combination, you'll want to set
> >> max_standby_archive_delay to a very low value, or a read-only query can
> >> cause master to stop processing commits (or the standby to stop
> >> accepting new queries, if that's preferred).
> >
> > Well, given that DML-only transactions aren't prone such to conflicts, I
> > think of this as a corner case.
> 
> Yes they are. Any DML operation, and even read-only queries IIRC, can 
> trigger HOT pruning, which can conflict with a read-only query in a hot 
> standby. And then there's autovacuum which can cause conflicts in the 
> standby, even if no user transactions are running in the master.

I can confirm that SELECT can trigger HOT pruning, based on research for
my PG West MVCC talk.  Anything that does a tuple lookup can cause it
--- INSERT VALUES does not.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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