OK, when I plugged it in to the online advisor it suggested:
CREATE INDEX adv_number_type_data_type_id_url_status ON `testA`(`number`,`type`,`data_type`,`id`,`url`,`status`)
as a covering index. Could you try this one and see if it performs any better? – I’m not sure why your existing index wouldn’t be the best possible performing index so this is just confirmation really.
I assume you’ve checked your query plan and it is simply the index scan?
The query service doesn’t pre-compute results to return in a select (map/reduce or pre-computed views). The result set is computed each time you run a statement.
How many documents do you have indexed and how many distinct values are you expecting?
Presumably the time taken is all in the index scan according to the profile output? – Perhaps you could share the complete profile for your query?