Re: Discussion on missing optimizations

Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> writes:
> Robert Haas wrote:
>> One trick that some system use is avoid replanning as much as we do
>> by, for example, saving plans in a shared cache and reusing them even
>> in other sessions. That's hard to do in our architecture because the
>> controlling GUCs can be different in every session and there's not
>> even any explicit labeling of which GUCs control planner behavior. But
>> if you had it, then extra planning cycles would be, perhaps, more
>> tolerable.

> From my experience with Oracle I would say that that is a can of worms.

Yeah, I'm pretty suspicious of the idea too. We've had an awful lot of
bad experience with local plan caching, to the point where people wonder
why we don't just auto-replan every time. How would a shared cache
make that better? (Even assuming it was otherwise free, which it
surely won't be.)

regards, tom lane