Question

我在MySQL中有以下表格：

CREATE TABLE tweetdb(
       tweetid BIGINT(18) UNSIGNED NOT NULL, 
       userid INT(10) UNSIGNED NOT NULL, 
       timestamp CHAR(14), 
       tweet TEXT, 
       score TINYINT, 
  PRIMARY KEY(tweetid, userid)
) ENGINE=MYISAM PARTITION BY KEY(userid) PARTITIONS 101;

+-----------+---------------------+------+-----+---------+-------+
| Field     | Type                | Null | Key | Default | Extra |
+-----------+---------------------+------+-----+---------+-------+
| tweetid   | bigint(18) unsigned | NO   | PRI | NULL    |       |
| userid    | int(10) unsigned    | NO   | PRI | NULL    |       |
| timestamp | char(14)            | YES  |     | NULL    |       |
| tweet     | text                | YES  |     | NULL    |       |
| score     | tinyint(4)          | YES  |     | NULL    |       |
+-----------+---------------------+------+-----+---------+-------+
5 rows in set (0.29 sec)

此表中有2.1亿行。我的Undertow服务器（Java应用程序）使用以下选择查询发送GET：

"SELECT test.tweetdb.tweetid, test.tweetdb.tweet, test.tweetdb.score FROM test.tweetdb WHERE test.tweetdb.userid = 287543000 AND test.tweetdb.timestamp = 20140420000829;"

我使用userid和timestamp来获取结果，因为它只是我可用于测试数据库的数据。该数据库仅用于读取目的，没有写入/更新。

我还在桌子上使用过索引。

mysql> SHOW INDEX FROM tweetdb;
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| tweetdb |          1 | id_index |            1 | userid      | A         |           1 |     NULL | NULL   | YES  | BTREE      |         |               |
| tweetdb |          1 | id_index |            2 | timestamp   | A         |           1 |     NULL | NULL   | YES  | BTREE      |         |               |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
2 rows in set (0.00 sec)

现在，即使在使用分区并应用主键之后，也需要将近1秒的时间来响应正确的响应，这非常长。我的应用程序必须具有每秒至少6000个请求的吞吐量。

硬件配置：

我正在运行Undertow服务器（前端）来查询Amazon M1.large实例上的Mysql服务器（后端）。为了避免延迟，我在同一个实例上运行两个服务器。

任何人都可以帮助我吗？我的想法不多了。谢谢！

更新

mysql> EXPLAIN SELECT * FROM test.tweetdb LIMIT 1;
+----+-------------+---------+------+---------------+------+---------+------+-----------+-------+
| id | select_type | table   | type | possible_keys | key  | key_len | ref  | rows      | Extra |
+----+-------------+---------+------+---------------+------+---------+------+-----------+-------+
|  1 | SIMPLE      | tweetdb | ALL  | NULL          | NULL | NULL    | NULL | 270119913 |       |
+----+-------------+---------+------+---------------+------+---------+------+-----------+-------+
1 row in set (3.67 sec)


mysql> EXPLAIN SELECT * FROM test.tweetdb WHERE test.tweetdb.userid=287543000 AND test.tweetdb.timestamp=20140420000829;
+----+-------------+---------+------+---------------+------+---------+------+---------+-------------+
| id | select_type | table   | type | possible_keys | key  | key_len | ref  | rows    | Extra       |
+----+-------------+---------+------+---------------+------+---------+------+---------+-------------+
|  1 | SIMPLE      | tweetdb | ALL  | NULL          | NULL | NULL    | NULL | 2657601 | Using where |
+----+-------------+---------+------+---------------+------+---------+------+---------+-------------+
1 row in set (0.00 sec)

来自Undertow前端服务器的时间

The time it takes is 1.3 seconds

Answer 1

您的主键是tweetid和userid的组合。对于mysql，它将进行全面搜索，因为您的表具有组合列的主键。您可以创建仅具有userid的另一个密钥。对于mysql，如果你在密钥中有两列，那么它们应该出现在它认为是整个表搜索的地方

非常慢的MySQL读取性能

1 个答案: