> > > > Do you consider using hash tables? > > Doubt it's really worth it, unless there's some way to amortize the > setup cost across multiple selectivity estimations; which would surely > complicate life. > MCV lists are updated only during "analyze" phase, don't they? If the "setup cost" is the cost of maintaining those "hash tables", it is not going to hurt much.
> > One thing that just now occurred to me is that as long as we maintain > the convention that MCV lists are in decreasing frequency order, one can > take any prefix of the list and it's a perfectly good MCV list of less > resolution. So one way to reduce the time taken in eqjoinsel is to set > an upper limit on the number of entries considered *by that routine*, > whereas other estimator functions could use larger lists. That makes sense, however, linear search for single item in the list of 10'000 elements could take a while. Hash lookup might be better choice. Regards, Vladimir Sitnikov
