Le Vendredi 25 Octobre 2002 20:17, Stephan Szabo a écrit :
> On Fri, 25 Oct 2002, [iso-8859-15] Hervé Piedvache wrote:
> > Thanks for you help ... to "explain" us why Postgresql do not use all the
> > time the index scan for this kind of request for 3 tables with the same
> > primary key id.
>
> Depending on the number of rows returned, index scan may not be faster
> than a sequential scan. As you up the constant, the estimated number of
> rows drops which make the index scan a better and better plan. Are
> the estimated number of rows for the scan of a (4379, 3987, and 29)
> realistic for mynumber>(23000, 23500, 24000)
I'm surpise about this answer for
>23000
result is 98
>23350
result is 96
>24000
result is 93
With a table of 471 413 records and most of the values for mynumber are
< of 2500 result is 467 902 records ...
I do not understand the explain result sorry ! ;o/
Regards,
--
Hervé Piedvache
Elma Ingénierie Informatique
6 rue du Faubourg Saint-Honoré
F-75008 - Paris - France
Tel. 33-144949901
fax. 33-144949902
