Re: JDBC, prepared queries, and partitioning

Simon Riggs wrote
> On Thu, 2008-02-14 at 10:45 +1300, Stephen Denne wrote:
> > Simon Riggs wrote
> > > ISTM we need a way to say "this query's parameters vary wildly at
> > > execution time, so I really need to re-plan it every time".
> >
> > If the wild variations don't affect the cost estimate, they
> won't affect the plan?
>
> Cost estimates are made at planning time. If you don't
> replan, no, they
> won't.

What I meant was that for some queries, replanning with wildly different parameter values will always select the same plan.
That'd happen if the distribution from which the parameter value is chosen was flat, and the operation involving the parameter doesn't affect selectivity (eg "equals" rather than "greater than").
Though I guess in that case that it isn't possible to have a "wildly" different value.

Stephen Denne.

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