On Wed, 2008-06-25 at 23:34 -0400, Robert Haas wrote:
> I can predict that Tom will say that the planning time it would take
> to avoid this problem isn't justified by the number of queries that it
> would improve.
> That's possible, but it's unfortunate that there's no
> way to fiddle with the knobs and get the planner to do this kind of
> thing when you want it to.
I don't think we should invent a new parameter for each new
optimisation. We would soon get swamped.
IMHO we should have a single parameter which indicates how much planning
time we consider acceptable for this query. e.g.
optimization_level = 2 (default), varies 1-3
Most automatic optimisation systems allow this kind of setting, whether
it be a DBMS, or compilers (e.g. gcc).
We should agree a simple framework so that each new category of
optimization can be described as being a level X optimisation, or
discarded as being never worth the time. We do this with error messages,
so why not do this with something to control planning time?
-- Simon Riggs www.2ndQuadrant.comPostgreSQL Training, Services and Support