| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Roland Roberts <roland(at)astrofoto(dot)org>, pgsql-jdbc(at)postgresql(dot)org |
| Subject: | Re: Very strange performance decrease when reusing a PreparedStatement |
| Date: | 2009-05-07 08:45:51 |
| Message-ID: | 1241685951.6109.70.camel@ebony.2ndQuadrant |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-jdbc |
On Wed, 2009-05-06 at 18:39 -0400, Tom Lane wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> > We talked a few years back about an "Option node" that would select
> > sub-plans at runtime based upon the actual values of the bind variable.
> > Nobody's got around to doing anything with that yet.
>
> There is an AlternativeSubPlan mechanism in 8.4, though we're not doing
> very much with it yet.
OK, good. We just need to use it when the distribution of values is
highly non-uniform such that values with max and min selectivity can
generate different plans *and* we have a parameter, the arrival
distribution of which we have no way of knowing at plan time. That case
accounts for about 50% of the cases for which hints/special handling is
currently required.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Oliver Hitz | 2009-05-07 11:59:19 | Re: Thread hangs in VisibleBufferedInputStream.readMore |
| Previous Message | Oliver Jowett | 2009-05-07 07:29:11 | Re: Thread hangs in VisibleBufferedInputStream.readMore |