Mark Kirkwood <mark.kirkwood@catalyst.net.nz> writes:
> While this is still fresh in your mind, a couple of additional anti join
> queries are still managing to sneak past estimation:
Yeah, those are estimating that all the outer rows have join partners,
because there are more distinct values in the sub-select than there are
in the outer relation. AFAICS there are not any errors in the
statistics, it's just that the estimation rule falls down here.
If you've heard of a better estimator for semijoin/antijoin selectivity,
I'm all ears. The best idea I have at the moment is to put an arbitrary
upper limit on the estimated selectivity, but that would be, well,
arbitrary.
regards, tom lane
