Re: Turning off HOT/Cleanup sometimes

On 2015-04-16 10:20:20 -0300, Alvaro Herrera wrote:
> I think you're failing to consider that in the patch there is a
> distinction between read-only page accesses and page updates.  During a
> page update, HOT cleanup is always done even with the patch, so there
> won't be any additional bloat that would not be there without the
> patch.

That's not really true (and my benchmark upthread proves it). The fact
that hot pruning only happens when we can get a cleanup lock means that
we can end up with more pages that are full, if we prune on select less
often. Especially if SELECTs are more frequent than write accesses -
pretty darn common - the likelihood of SELECTs getting the lock is
correspondingly higher.

Greetings,

Andres Freund

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