Re: Major differences between oracle and postgres performance - what can I do ?

Stephen Frost <sfrost@snowman.net> writes:
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>> [... thinks for awhile ...]  It seems possible that they may use sort
>> code that knows it is performing a DISTINCT operation and discards
>> duplicates on sight.  Given that there are only 534 distinct values,
>> the sort would easily stay in memory if that were happening.

> Could this optimization be added to PostgreSQL?  It sounds like a very
> reasonable thing to do.

That's what I was wondering about too.  But first I'd like to get
some kind of reading on how effective it would be.  If someone can
demonstrate that Oracle can do sort-and-drop-dups a lot faster than
it can do a straight sort of the same amount of input data, that
would be a strong indication that it's worth doing.  At this point
we don't know if that's the source of their win or not.

            regards, tom lane