Re: Unexpected benchmark results due to query optimizer?

[Jay Pipes]

The only thing I can think of is that at this specific point, the b-tree must be branched (as opposed to containing all index records in the root node? Perhaps that is why there is a small dip in the performance results?

Once a certain threshold is reached, perhaps MyISAM (I've assumed you're using MyISAM...) does indeed change strategies (regardless of whether the key block is in the key cache or not) in order to find the appropriate index record. To find the answer, you'll have to either ask one of the developers or go into the source code to find the answers...

Good luck, and good observations,

Jay Pipes
Community Relations Manager, North America, MySQL Inc.

Got Cluster? http://www.mysql.com/cluster
Personal: http://jpipes.com