Re: Statistics on Indexes

So you want to change from RULE to COST but are afraid your performance might collaps?

I'm not going to try to give my opinion on all what you've brought up, but I will tell you what I've come across.

When you go from RULE to COST performance tends to get better. The only cases I've had seen it degrade is when the WHERE clause contains an equation of a column with a literal with a value that is very rare for that column in the database. RULE would have used the index and COST should have too, but the different values of the column are assumed by the optimizer to be distributed evenly. If a value is rare and that is important to know you should make a histogram of the column (part of the ANALYZE command).

Maybe someone else has other examples, I curious (in fact I'll start an seperate thread).

Jaap Received on Sat Feb 05 2000 - 06:25:37 CST