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.