Re: Persistent Plan Cache

Tom Lane wrote:
> Joshua Rubin <jrubin(at)esoft(dot)com> writes:
>> We have a very large, partitioned, table that we often need to query
>> from new connections, but frequently with similar queries. We have
>> constraint exclusion on to take advantage of the partitioning. This also
>> makes query planning more expensive. As a result, the CPU is fully
>> loaded, all the time, preparing queries, many of which have been
>> prepared, identically, by other connections.
>
> If you're depending on constraint exclusion, it's hard to see how plan
> caching could help you at all. The generated plan needs to vary
> depending on the actual WHERE-clause parameters.

That's what the OP really should've complained about. If we addressed
that, so that a generic plan was created that determines which child
tables can be excluded at run time, there would be no need for the
persistent plan cache.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com