資料更新導致鎖表
一、資料表結構
12345678910 | CREATE TABLE `jx_attach` ( `attach_id` int (11) NOT NULL AUTO_INCREMENT, `feed_id` int (11) DEFAULT NULL , `attach_name` varchar (255) NOT NULL , `cycore_file_id` varchar (255) DEFAULT NULL , `attach_size` bigint (20) NOT NULL DEFAULT '0' , `complete` smallint (6) NOT NULL DEFAULT '0' , PRIMARY KEY (`attach_id`), KEY `jx_trend_attach_FK` (`feed_id`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=394160 DEFAULT CHARSET=utf8; |
二、現象
當多個連線同時對一個表的資料進行更新操作,那麼速度將會越來越慢,持續一段時間後將出現資料表被鎖,從而影響到其它的查詢及更新。
儲存過程迴圈30次更新操作
12345678 | /*30次更新操作*/ BEGIN DECLARE v1 INT DEFAULT 30; WHILE v1 > 0 DO update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; SET v1 = v1 - 1; END WHILE; END |
執行結果(速度非常慢)
時間: 29.876s
Procedure executed successfully
受影響的行: 0
200個數據更新操作,三個資料庫連線同時執行
1234567 | update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; update jx_attach set complete=1,attach_size=63100 where cycore_file_id= '56677142da502cd8907eb58f' ; ...等等 |
執行結果(持續一段時間後速度越來越慢,出現等待鎖)
# Time: 151208 22:41:24
# [email protected]: zmduan[zmduan] @ [192.168.235.1] Id: 2
# Query_time: 1.848644 Lock_time: 0.780778 Rows_sent: 0 Rows_examined: 393382
SET timestamp=1449643284;
update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
.........
........
# User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 2 # Query_time: 2.868598 Lock_time: 1.558542 Rows_sent: 0 Rows_examined: 393382 SET timestamp=1449643805; update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f'; [[email protected] log]# tail -f slow_query.log # User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 19 # Query_time: 1.356797 Lock_time: 0.000169 Rows_sent: 1 Rows_examined: 393383 SET timestamp=1449643805; SELECT * FROM jx_attach ja,jx_feed jf where ja.feed_id=jf.feed_id and ja.cycore_file_id='56677146da502cd8907eb5b7'; # User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 2 # Query_time: 2.868598 Lock_time: 1.558542 Rows_sent: 0 Rows_examined: 393382 SET timestamp=1449643805; update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
三、原因分析
MySQL的innodb儲存引擎支援行級鎖,innodb的行鎖是通過給索引項加鎖實現的,這就意味著只有通過索引條件檢索資料時,innodb才使用行鎖,否則使用表鎖。根據當前的資料更新語句(update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';),該條件欄位cycore_file_id並沒有新增索引,所以導致資料表被鎖。
四、解決辦法
為cycore_file_id新增索引
五、最終效果(30次更新操作)
時間: 0.094s
Procedure executed successfully
受影響的行: 0