Re: Cost-based Optimizers

Wieslaw Poszewiecki writes:
>My knowledge about the topic is not most up to date. But as far as
>I know Ingres has implemented histograms. INGRES engine
>knows not only of how many rows does table have, but also what is the density
>of rows in some interval of index values. Informix engines generally
>speaking know how many rows does table have and what indices are built.

As of version 6.0, OnLine also optionally maintains distributions info, essentially the same as histograms. There is a great deal of flexibility with these, allowing you to specify sampling rates, what columns to maintain distributions on, etc.

-- 
Dave Kosenko
Disclaimer: The opinions expressed in this message are not those of Informix 
Software, its partners or lackeys.  Anyone who says otherwise is itching for 
a fight.