I think MySQL just need to read the B-Tree index for this count(*).
On 01/09/2011 11:41 PM, Sergei Golubchik wrote:
> Hi, ??????!
> On Jan 09, ?????? wrote:
>> 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 thousandes of lines from the storage engine, this is a
>> time-consuming operation.
>> If tell the storage engine computing the count in the range, does it
>> have higher performance? (using records_in_range() api and so on)
> There's no API for that in MySQL yet.
> records_in_range() is approximate, it cannot be used for count(*).
MySQL& Oracle Data Architecture