Re: Performance on inserts

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> What I am more concerned about is a join that uses the most common
> value.  We do an index scan in that case.

No, we do whichever plan looks cheapest.  Again, it's all about
statistics.

Right now, eqjoinsel() is just a stub that returns a constant
selectivity estimate.  It might be useful to compute some more
sophisticated value based on pg_statistic entries for the two
columns, but right now I doubt you could tell much.  Should keep
the join case in mind when we extend the statistics...
        regards, tom lane