On 17 Jul 2003 at 14:50, Fabian Kreitner wrote:

> At 14:34 17.07.2003, you wrote:
> >I expect you will find that the third query is also a lot faster that the 
> >first query.
> Im afraid, no.
> Database has been stopped / started right before this.
> perg_1097=# set enable_seqscan to true;
> perg_1097=# EXPLAIN ANALYZE    select  notiz_id, obj_id, obj_typ
> perg_1097-#      from    notiz_objekt a
> perg_1097-#      where not exists

Well, he said query and not the query plan...:-) 

While explain analyze is great for judging what is happening, it's not always a 
good idea to trust the numbers produced by it. It will probably produce same 
number for a SCSI disk machine and for a IDE disk machine, everything else 
being equal. Obviously that is not correct.

Only thing you can trust in explain analyze is it's plan. Numbers are based on 
heuristic and should be taken as hint only.


Harrisberger's Fourth Law of the Lab:   Experience is directly proportional to 
the amount of equipment ruined.

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