Re: Prepared statements and suboptimal plans

Andy Lester <andy@petdance.com> writes:
> On Sep 20, 2011, at 7:36 PM, Tom Lane wrote:
>> 9.2, sorry, not 9.1.  We could use some motivated people testing that
>> aspect of GIT HEAD, though, since I doubt the policy for when to re-plan
>> is quite ideal yet.

> Is motivation and a box enough?  I have motivation, but not knowledge of internals enough to drive testing myself.

Well, you probably don't need much internals knowledge as long as you
can read a little C.  The crux of what I'm worried about is
choose_custom_plan() in src/backend/utils/cache/plancache.c, which is
really pretty simple: decide whether to use a custom (parameter-aware)
plan or a generic (not-parameter-aware) plan.  You might want to shove
some elog() calls in there for tracing purposes so that you can log what
it did, but then it's just a matter of throwing real-world workloads at
it and seeing if it makes good decisions.

            regards, tom lane