>> The existing cost estimation
>> code effectively assumes that they're perfectly uniformly distributed;
>> which is a good average-case assumption but can be horribly wrong in
>> the worst case.
Sorry, just an outsider jumping in with a quick comment.
Every year or two the core count goes up. Can/should/does postgres ever attempt two strategies in parallel, in cases
wherestrategy A is generally good but strategy B prevents bad worst case behaviour? Kind of like a Schrödinger's Cat
approachto scheduling. What problems would it raise?
Graeme.