我有这个查询的问题:
SELECT
uca.user_activity_id,
uca.user_call_id,
uca.call_activity_id,
uca.user_activity_token,
uc.call_group_id,
uc.user_id
FROM users_calls_activities uca
INNER JOIN users_calls_activities uca2 ON uca2.user_activity_id = uca.user_activity_is_validated_with
AND aux.user_call_id = 1744136
INNER JOIN users_calls uc ON uc.user_call_id = uca.user_call_id;
我们有一个带有percona服务器的集群(5.6.29),在Azure中有5个节点(从0到4).节点0-3和4之间的区别在于,第一个节点在平衡器中,节点4在平衡器之外(但在集群中)
问题是在四个服务器(节点0-3)中查询真的很慢(15秒)而在另一个(节点4)中查询真的很快(0,002)
Afaik,解释计划应该是相同的,但我执行一个EXPLAIN,结果是这样的:
节点0-3(慢)
+----+-------------+-------+------+-------------------------------------------------------------+--------------+---------+-------------------------------+---------+---------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------+--------------+---------+-------------------------------+---------+---------------------------------------+ | 1 | SIMPLE | uca2 | ref | PRIMARY,user_call_id,user_call_id_2 | user_call_id | 4 | const | 1 | Using index | | 1 | SIMPLE | uc | ALL | PRIMARY,user_call_id | NULL | NULL | NULL | 2098152 | Using join buffer (Block Nested Loop) | | 1 | SIMPLE | uca | ref | user_call_id,user_call_id_2,is_validated_with | user_call_id | 4 | db.uc.user_call_id | 1 | Using where | +----+-------------+-------+------+-------------------------------------------------------------+--------------+---------+-------------------------------+---------+---------------------------------------+
节点4(快速)
+----+-------------+-------+--------+-------------------------------------------------------------+---------------------------------+---------+-----------------------------------+---------+-----------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-------------------------------------------------------------+---------------------------------+---------+-----------------------------------+---------+-----------------------+ | 1 | SIMPLE | uca2 | ref | PRIMARY,user_call_id,user_call_id_2 | user_call_id | 4 | const | 1 | Using index | | 1 | SIMPLE | uca | ref | user_call_id,user_call_id_2,is_validated_with | is_validated_with | 5 | db.uc2.user_activity_id | 2755595 | Using index condition | | 1 | SIMPLE | uc | eq_ref | PRIMARY,user_call_id | PRIMARY | 4 | db.uca.user_call_id | 1 | NULL | +----+-------------+-------+--------+-------------------------------------------------------------+---------------------------------+---------+-----------------------------------+---------+-----------------------+
我注意到在慢速中索引没有被使用.所以我检查了索引:
节点0:
+-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | users_calls | 0 | PRIMARY | 1 | user_call_id | A | 2099153 | NULL | NULL | | BTREE | | | | users_calls | 1 | call_group_id | 1 | call_group_id | A | 16659 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_call_begin_date | 1 | user_call_begin_date | A | 1049576 | NULL | NULL | YES | BTREE | | | | users_calls | 1 | user_call_begin_date | 2 | user_call_end_date | A | 2099153 | NULL | NULL | YES | BTREE | | | | users_calls | 1 | user_call_id | 1 | user_call_id | A | 2099153 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_call_id | 2 | user_id | A | 2099153 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 1 | user_id | A | 91267 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 2 | call_id | A | 2099153 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 3 | user_call_status | A | 2099153 | NULL | NULL | | BTREE | | | | users_calls | 1 | fk_users_calls_calls | 1 | call_id | A | 23067 | NULL | NULL | | BTREE | | | +-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
节点4:
+-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | users_calls | 0 | PRIMARY | 1 | user_call_id | A | 2091476 | NULL | NULL | | BTREE | | | | users_calls | 1 | call_group_id | 1 | call_group_id | A | 26813 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_call_begin_date | 1 | user_call_begin_date | A | 1045738 | NULL | NULL | YES | BTREE | | | | users_calls | 1 | user_call_begin_date | 2 | user_call_end_date | A | 2091476 | NULL | NULL | YES | BTREE | | | | users_calls | 1 | user_call_id | 1 | user_call_id | A | 2091476 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_call_id | 2 | user_id | A | 2091476 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 1 | user_id | A | 53627 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 2 | call_id | A | 2091476 | NULL | NULL | | BTREE | | | | users_calls | 1 | user_id | 3 | user_call_status | A | 2091476 | NULL | NULL | | BTREE | | | | users_calls | 1 | fk_users_calls_calls | 1 | call_id | A | 15608 | NULL | NULL | | BTREE | | | +-----------------+------------+----------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
我的第一个问题是为什么索引不同？它应该是相同的,因为两者都在同一个集群中吗？
为什么执行计划不同？两者都在同一个集群中,所以它应该是相同的
我应该使用FORCE INDEX或STRAIGHT_JOIN？
小智 0
我认为两个表上都有 user_call_id 字段。如果您像这样更改查询，它将强制服务器使用索引：
SELECT
uca.user_activity_id,
uca.user_call_id,
uca.call_activity_id,
uca.user_activity_token,
uc.call_group_id,
uc.user_id
FROM users_calls_activities uca
INNER JOIN users_calls_activities uca2 ON uca2.user_activity_id = uca.user_activity_is_validated_with AND uca2.user_call_id = 1744136
INNER JOIN users_calls uc ON uc.user_call_id = uca.user_call_id uc.user_call_id = 1744136
WHERE uca.user_call_id = 1744136;