Re: Major differences between oracle and postgres performance - Mailing list pgsql-performance

Gary Cowell wrote:
> The explain output on postgres shows the same
> execution with a scan on vers and a sort but the query
> time is 78.6 seconds.
>
> The explain output from PostgreSQL is:
>                                    QUERY PLAN
> ---------------------------------------------------------------------------------
>  Unique  (cost=117865.77..120574.48 rows=142
> width=132)
>    ->  Sort  (cost=117865.77..119220.13 rows=541741
> width=132)
>          Sort Key: "version"
>          ->  Seq Scan on vers  (cost=0.00..21367.41
> rows=541741 width=132)
>                Filter: ("version" IS NOT NULL)
>
> I do have an index on the column in question but
> neither oracle nor postgresql choose to use it (which
> given that we're visiting all rows is perhaps not
> surprising).

Can you post explain analyze for the same query? It contains actual numbers
alond side the chosen plan.

>
> I'm not as familiar with postgresql as I am with
> Oracle but I think I've configured comparible
> buffering and sort area sizes, certainly there isn't
> much physical IO going on in either case.

Well, for postgresql you should check out

http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html
http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html

HTH

  Shridhar