How can I impove this JOIN operation between key table and another - mysql

Question

My problem is that I have two different queries that work well in different
situations.
SCHEMA
messages
message_id, entity_id, message, timestamp
subscription
user_id, entity_id
users
user_id
entities
entity_id
Situation 1: Lots of message entries, and at least one relevant subscription entry
Situation 2: Few message entries and/or few, or zero, subscription entries that are relevant
My Two Queries are:
SELECT messages.*
FROM messages
STRAIGHT_JOIN subscription ON subscription.entity_id = messages.entity_id
WHERE subscription.user_id = 1
ORDER BY messages.timestamp DESC
LIMIT 50
This query works well in situation 1 (.000x seconds): Lots of message entries, and at least one relevant subscription entry. thisquery will take 1.7+ seconds in situation 2.
SELECT messages.*
FROM messages
INNER JOIN subscription ON subscription.entity_id = messages.entity_id
WHERE subscription.user_id = 1
ORDER BY messages.timestamp DESC
LIMIT 50
This query works well in situation 2 (.000x seconds): Few message entries and/or few, or zero, subscription entries that are relevant. This query will take 1.3+ seconds in situation 1.
Is there a query that I can use that can get the best of both worlds? If not, what's the best way to
handle this case?
Indexes:
( subscription.user_id, subscription.entity_id )
( subscription.entity_id )
( messages.entity_id, messages.timestamp )
( messages.timestamp )
EXPLAIN INFO
LIMIT 50
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
| 1 | SIMPLE | messages | index | idx_timestamp | idx_timestamp | 4 | NULL | 50 | |
| 1 | SIMPLE | subscription | eq_ref | PRIMARY,entity_id,user_id | PRIMARY | 16 | const, messages.entity_id | 1 | Using index |
Without Limit
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
| 1 | SIMPLE | messages | ALL | entity_id_2,entity_id | NULL | NULL | NUL | 255069 | Using filesort|
| 1 | SIMPLE | subscription | eq_ref | PRIMARY,entity_id,user_id | PRIMARY | 16 | const, messages.entity_id | 1 | Using index |
CREATE TABLE STATEMENTS:
With ~5000 rows
subscription | CREATE TABLE `subscription` (
`user_id` bigint(20) unsigned NOT NULL,
`entity_id` bigint(20) unsigned NOT NULL,
PRIMARY KEY (`user_id`,`entity_id`),
KEY `entity_id` (`entity_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
with ~255,000 rows
messages | CREATE TABLE `messages` (
`message_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`entity_id` bigint(20) unsigned NOT NULL,
`message` varchar(255) NOT NULL DEFAULT '',
`timestamp` int(10) unsigned NOT NULL,
PRIMARY KEY (`message_id`),
KEY `entity_id` (`entity_id`,`timestamp`),
KEY `idx_timestamp` (`timestamp`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

Answer 1

Try changing your WHERE with a AND
SELECT messages.*
FROM messages
STRAIGHT_JOIN subscription ON subscription.entity_id = messages.entity_id
AND subscription.user_id = 1
ORDER BY messages.timestamp DESC
LIMIT 50
OR
SELECT messages.*
FROM messages
INNER JOIN subscription ON subscription.entity_id = messages.entity_id
AND subscription.user_id = 1
ORDER BY messages.timestamp DESC
LIMIT 50
OR may be this way :
SELECT messages.*
FROM subscription
STRAIGHT_JOIN messages ON subscription.entity_id = messages.entity_id
WHERE subscription.user_id = 1
ORDER BY messages.timestamp DESC
LIMIT 50