Re: Speed comparison to Oracle. Why was this query slower

Tom Lane wrote:
> Martijn van Oosterhout <kleptog@svana.org> writes:
> > On Fri, Feb 22, 2002 at 05:23:40PM -0500, Francisco Reyes wrote:
> >>> Is Oracle better at aggregate functions?
> >> How could it be done in a more clever fashion?
>
> > By hashing. Get a hash table. For each row, hash the grouping rows to lookup
> > the intermediate aggregate stage to aggregate this row into. At the end, run
> > through your hash dumping the results.
>
> This is on our TODO list.  It'd be interesting to know whether that is
> the source of Oracle's speed advantage in this particular scenario,
> though.  What is PG's EXPLAIN output for this query, and what does
> Oracle have to say about it?  (They don't call it EXPLAIN, but I know
> they have an equivalent function to show the query plan for a query.)

Was the original users doing GROUP BY with the aggregate?  I don't
remember.

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