In the last episode (Nov 21), johnt@stripped said:
> Adding an irrelevant second column to an index instead of just a
> single column index gives an incredible speedup and I don't know why!
If you then remove the index, is it still fast? Maybe you are just
seeing the results of mysql rebuilding the state key. When you modify
an index, I believe mysql ends up rebuilding all indexes on that table.
"optimize table mytable" would probably have given you the same speed