Hi Gunnar, I agree, this should be optimized.
It says in the Internals manual, I believe, that the code already exists (in what version(s) I don't know) to optimize such searches on multiple indexes but it just isn't implemented yet. Hopefully it will be soon... Matt ----- Original Message ----- From: "Boehn, Gunnar von" Sent: Tuesday, November 18, 2003 4:23 AM Subject: Feature wish > Hi, > > I wonder if a small enhancement to the > mysql planner/optimizer could be made. > > > The current (mysql4.0) optimizer only uses one index per SELECT. > Because of this some queries result in a slow fulltable scan > even if all used columns are indexed. > > Example: > SELECT * FROM table1 WHERE columnA='x' OR columnB='x' > (Slow table scan even if columnA and columnB are indexd! > Other Databases like PostgreSQL don't have this problem.) > > > Since Mysql 4.0 a UNION can be used to speed this up. > > Example: > SELECT * FROM table1 WHERE columnA='x' > UNION SELECT * FROM table1 WHERE columnB='x' > (Now we have two SELECT with one index each.) > > > Couldn't the planner/optimizer be easely changed to do this UNION > automaticly ? > > > I think this would be a big improvement to mysql. > > If I port applications from other databases to mysql > there are often queries like this. Either those queries > run terrible slow an mysql or I have to manually convert them into UNIONs. > > > Thanks in advance > Gunnar -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
