Optimize MAX msg_uid query

[thomasst]

EXPLAIN ANALYZE SELECT max(imapuid.msg_uid) AS max_1 
FROM imapuid FORCE INDEX (ix_imapuid_account_id_folder_id_msg_uid_desc) 
WHERE imapuid.account_id = 42791 AND imapuid.folder_id = 464285;

-> Aggregate: max(imapuid.msg_uid)  (cost=921858 rows=1) (actual time=999..999 rows=1 loops=1)↵    -> Covering index lookup on imapuid using ix_imapuid_account_id_folder_id_msg_uid_desc (account_id=42791, folder_id=464285)  (cost=464365 rows=4.57e+6) (actual time=0.664..830 rows=2.03e+6 loops=1)↵


EXPLAIN ANALYZE SELECT msg_uid
FROM imapuid FORCE INDEX (ix_imapuid_account_id_folder_id_msg_uid_desc)
WHERE account_id = 42791 AND folder_id = 464285
ORDER BY msg_uid DESC LIMIT 1;

-> Limit: 1 row(s)  (cost=33 rows=1) (actual time=0.0359..0.036 rows=1 loops=1)↵    -> Covering index lookup on imapuid using ix_imapuid_account_id_folder_id_msg_uid_desc (account_id=42791, folder_id=464285)  (cost=33 rows=321) (actual time=0.0354..0.0354 rows=1 loops=1)↵