MySQL通過添加索引解決線上數據庫服務器壓力大問題
阿新 • • 發佈:2018-03-27
索引 MySQL 監控 無法登陸無法打開網頁 昨天線上應用反饋晚上 19:30-19:43以及 20:13到20:21兩個時間段所有人包括我們自己建的教室都進不去,
classroom B套無法登陸,主頁無法訪問,已有超過10個老師和學生反饋進不去教室的問題
通過監控查看出現問題時數據庫服務器的cpu使用率,負載,io,內存使用,swap剩余量等狀況,發現數據庫當時壓力特別大,
數據庫連接數:
數據庫慢查詢也出現很多
查看慢查詢日誌,發現一個SQL在慢查詢日誌中頻繁出現切執行時間較長
# User@Host: cms[cms] @ [172.17.43.24] # Query_time: 10.252490 Lock_time: 0.000052 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2680447 )and(participan0_.pin='1219' ); # User@Host: cms[cms] @ [172.17.43.25] # Query_time: 10.297055 Lock_time: 0.000050 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2697493 )and(participan0_.pin='1492' ); # User@Host: cms[cms] @ [172.17.43.25] # Query_time: 10.319839 Lock_time: 0.000048 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2680355 )and(participan0_.pin='9590' ); # User@Host: cms[cms] @ [172.17.43.24] # Query_time: 10.163372 Lock_time: 0.000063 Rows_sent: 1 Rows_examined: 2345872 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2731041 )and(participan0_.pin='1506' ); # User@Host: cms[cms] @ [172.17.43.24] # Query_time: 9.950549 Lock_time: 0.000073 Rows_sent: 1 Rows_examined: 2345881 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2682013 )and(participan0_.pin='6086' ); # User@Host: cms[cms] @ [172.17.43.25] # Query_time: 9.992145 Lock_time: 0.000051 Rows_sent: 1 Rows_examined: 2345879 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2697493 )and(participan0_.pin='1103' );
查看該SQL的執行計劃發現走了全表掃描,掃描了200多萬行的數據;
mysql> explain select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_.pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefine9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from participant participan0_ where (participan0_.conferenceid=2724963 )and(participan0_.pin='5476' ); +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ | 1 | SIMPLE | participan0_ | ALL | NULL | NULL | NULL | NULL | 2042005 | Using where | +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ 1 row in set (0.02 sec)
發現該表where條件的列上沒有索引:
mysql> show index from participant; +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | participant | 0 | PRIMARY | 1 | id | A | 2384122 | NULL | NULL | | BTREE | | | +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 1 row in set (0.00 sec)
和發開溝通後在該表上加上以下索引:
mysql> ALTER TABLE `participant` ADD INDEX index_conferenceid (`conferenceid`); Query OK, 0 rows affected (9.16 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE `participant` ADD INDEX index_pin (`pin`); Query OK, 0 rows affected (6.96 sec) Records: 0 Duplicates: 0 Warnings: 0
再次查看該SQL的執行計劃:
mysql> explain select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_.pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefine9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from participant participan0_ where (participan0_.conferenceid=2724963 )and(participan0_.pin='5476' ); +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ | 1 | SIMPLE | participan0_ | index_merge | index_conferenceid,index_pin | index_conferenceid,index_pin | 5,7 | NULL | 1 | Using intersect(index_conferenceid,index_pin); Using where | +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ 1 row in set (0.01 sec)
-----------------------------我是分割線-----------------------
等到晚上約課較多的時間再次觀察數據庫的負載和慢查詢日誌
MySQL通過添加索引解決線上數據庫服務器壓力大問題