How to optimize COUNT(*) performance on InnoDB by using index

Question

I have a largish but narrow InnoDB table with ~9m records. Doing count(*) or count(id) on the table is extremely slow (6+ seconds):

Answer 1

For the time being I've solved the problem by using this approximation:

EXPLAIN SELECT COUNT(id) FROM data USE INDEX (PRIMARY)

The approximate number of rows can be read from the rows column of the explain plan when using InnoDB as shown above. When using MyISAM this will remain EMPTY as the table reference isbeing optimized away- so if empty fallback to traditional SELECT COUNT instead.