mysql - ORDER on Boolean field much slower than order on PK -

I am doing a query that orders the result on a Boolean field (TINITT (1)). It has been indexed.

from the 'main list' from the list 'Select' from the 'main' list. `_________ 'ASC limit1

It takes 1.61 seconds to run. If I do the same query without the ORDER BY , it takes a fraction of the time:

'code> SELECT * to' main_catalog 'LIMIT 1

It takes 4.1ms to complete. Why does it take too much time to do it on a Boolean field on PK?

Why does it take so much time to sort on boolean field over a PK?

It is easy to have an index in the primary key that makes it possible to get a record in sequential order without doing any of the following. You have a simple query, so this index can be used for retrieval. is. (An additional customization is because the rows are in the primary key sequence, but this is a small additional advantage than being an index.)

You can create an index at main_catalog (is_tv_on_itunes) < / Code> or anything similar to additional fields.

And, for bus records only, query:

  SELECT * FROM 'main_catalog` LIMIT 1  

on the primary key No sort results in a given query are not guaranteed to happen in a particular order if you want them in the primary key sequence, then the order statement to guarantee you Need to add