Re: Transaction Snapshots and Hot Standby

On Fri, 2008-09-12 at 12:25 +0100, Gregory Stark wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
> 
> > 3. Ignore problem
> > Effects:
> > * Long running queries on standby...
> >    Have no effect on primary
> >    Do not delay apply of WAL records on standby
> > * Queries on standby give inconsistent answers in some cases, though
> > doesn't generate any messages to show inconsistency occurred. Acceptable
> > for read-only and insert only tables only.
> 
> This seems like a non-starter. 

It works, and is proposed as a non-default option since a number of
people have independently said to me that this would be
acceptable/preferred.

> Your comment about read-only and insert-only tuples only seems to make sense
> if you assume there are other tables being updated simultaneously. Otherwise
> of course there would be no WAL records for tuple removals.

Yeh, you got it.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support