Thanks for the guidance and references, Shawn. On Wed, Jul 11, 2012 at 3:37 PM, Shawn Green <shawn.l.gr...@oracle.com> wrote: > > Ranged scans only happen for the last portion of an index being used. OR > queries (or those using IN) can also only be applied to the last part of an > index search. This means that if you are using IN (or OR) against the first > part of an index, that's where the usage of the index stops.
Basically, this is what I was expecting. However, in the second table in the join, the secondary column wasn't being used for the range or IN. I was expecting, given the nested-join loop algorithm (as I don't believe that BNL would be used http://dev.mysql.com/doc/refman/5.5/en/nested-loop-joins.html), that the first column in the key would be treated as const allowing the second column to be used in a range or IN criteria. > > Also, trying to force index usage may be creating more work for your disks > than necessary. I should have indicated in the original post that I was forcing the index simply to make the example work without data. Regards, Jeff -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql
