Re: Avoiding bad prepared-statement plans.

On Thu, Feb 25, 2010 at 22:11, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alex Hunsaker <badalex@gmail.com> writes:
> Uh, no, this isn't about saving either parse time or bandwidth.
> The discussion is about when to expend more planning time in hopes
> of getting better plans.

This is what im tripping over:

> > Bruce's suggestion that we should provide some user control over whether we plan at bind time or execute time

Let me see if I can sum up what I was trying to say:

Prepared plans + bind plan (what we have now):
  Use: when you have a query that takes a long time to plan
  Problems: if you use parameters you might no get a good plan
  Solution: if you have stable parameters dont pass them as such, inline them
  Better:  If we could figure out and make  we could make better plans
on the fly and use them

[ aka if you have a good driver you can easily control if its a
prepared statement or not without changing how you quote or inline
your sql ]

Prepared plans + exec plan (new guc/ protocol thing):
  Use: not quite sure
  Problems: slow because it would replan every time
  Solutions: use a prepared plan with the appropriate things not
parametrized...?

[ aka we already have this, its called dont use a prepared statement ]

Whats the benefit of prepare + exec plan vs just inlining?  What do
you save?  Some parse time?  Some bandwidth? Yeah if its a smart knob
that does things like "Oh, I see I have an mvc for that param, ill
give you a better plan".  OK, But the knob no longer means plan at
execute time.  It more in the realm of what Tom is suggesting IMHO.
Anyway I feel like im probably just violently agreeing.