RE: CBO - hash join vs nested loops
- From: "Christian Antognini" <Christian.Antognini@xxxxxxxxxxxx>
- To: "Radoulov, Dimitre" <cichomitiko@xxxxxxxxx>
- Date: Fri, 2 Dec 2005 18:54:20 +0100
Dimitre
>Checked the CDN and NDV for the tables/columns and they seem OK,
>but I have to check the indexes stats too.
Even if the object statistics are ok the CBO could do/apply a wrong
estimation...
>The only think I noticed is that the CBO expects 2076 rows before the final
>distinct and they are 1401.
And what do the following statements return?
select count(*)
from filtro_dati_catalogo
where id_subcatalogo in (0);
select count(*)
from opt_vp
where codice_opt = 29;
The idea is to know if it's wrong in computing the cardinality for the tables'
access or for the join. If the problem is at table level, a histogram could be
useful...
HTH
Chris
PS: even if my mother tongue is Italian, and I live in the Italian part of
Switzerland, this is the first time I see a schema with Italian names... Where
does such a schema come from?
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