Tom Lane wrote:
> Right, but if the parameter is unknown then its distribution is also
> unknown. In any case that's just nitpicking, because the solution is
> to create a custom plan for the specific value supplied. Or are you
> suggesting that we should create a way for users to say "here is the
> expected distribution of this parameter", and then try to fold that into
> the planner estimates?
Or instead of letting users give the distribution, gather it
automatically in some plan statistics catalog? I suspect in most
applications queries stay the same for months and maybe years, so after
some number of iterations it is possible to have decent call statistics
/ parameter distributions. Maybe the the parameter value distribution
could even be annotated with actual cached plans.
regards,
Yeb Havinga
