For example, we have t1 (id, name, addr) and its index table d1 (name).
if we do "select count(distinct name) from t1" while use-index is disabled, we get the correct result.
if we do the same query while index is enabled, we get a wrong result, which equals to "count(name)".
For example, we have t1 (id, name, addr) and its index table d1 (name).
if we do "select count(distinct name) from t1" while use-index is disabled, we get the correct result. if we do the same query while index is enabled, we get a wrong result, which equals to "count(name)".