| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
| Cc: | Francisco Reyes <lists(at)natserv(dot)com>, pgsql General List <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Speed comparison to Oracle. Why was this query slower on pgsql? |
| Date: | 2002-02-22 23:55:44 |
| Message-ID: | 21648.1014422144@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Martijn van Oosterhout <kleptog(at)svana(dot)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.)
regards, tom lane
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