Following your example :
So, table T has columns C1, C2, C3, C4 and two indexes: one on C1 and
one on C2, C3:

update statistics low for table T(C1);
update statistics low for table T(C2, C3);

would be the proper method to update stats low.

Update statistics low for table T(C1,C2,C3)
Would not update stats on any index?


regards



-----Mensaje original-----
De: Rob Wilson [mailto:rob_wilson@ameritech.net]
Enviado el: Viernes, 22 de Agosto de 2003 10:11 a.m.
Para: informix-list@iiug.org
Asunto: Re: UPDATE STATISTICS


Olivier CHRISTOL wrote:


> The update statistics low for a column does not update indexes whereas
> the low for the table do.
>

It is my understanding (but I have never tested) that if you have a
single-column index and you update stats low on that column, the stats
for that index are updated. It is my further understanding that for
multi-column indexes if you update stats low and list all the columns in
that index, the stats will be updated.

So, table T has columns C1, C2, C3, C4 and two indexes: one on C1 and
one on C2, C3:

update statistics low for table T(C1);
update statistics low for table T(C2, C3);

would be the proper method to update stats low.

I have further found (through experience and testing) that following the
recommendations in the Guide to Performance for your particular flavor
of Informix tends to both perform well when running and also cause good
performance for other queries. Yes, there are exceptions. Always test
first.
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