[Maria-developers] Optimization about count(*) of mysql 5.1.38

hi all: I have a question about the optimization of count(*) in a range. Sql for mysql like:select count(*) from t where id > 10 and id < 1000000; In table t, there is an B-tree index on id field, this sql will read hundreds of thousands of records from the storage engine, that is a time-consuming operation. I am developing a storage engine, I want to know, is there a good method to caculate the records in a range, rather than read all records or keys in the range? For example, does mysql call an API like records_in_range() to get the records in a range? After all, the range could be caculated by reading twice index.