昨天3月26號線上應用反饋：晚上19：30-19：43以及 20：13到20：21兩個時間段所有人包括他們自己建的教室都進不去，cla***oom 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26號00:00到27號11:00之間的監控，查看出現問題時數據庫服務器的cpu使用率，負載，內存使用，swap剩余量等狀況，發現數據庫當時壓力特別大，

數據庫慢查詢日志中出現很多慢SQL，

查看慢查詢日志，發現一個SQL在慢查詢日志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)

和開發溝通后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:?0mysql>?ALTER??TABLE??`participant`??ADD??INDEX?index_pin?(`pin`); Query?OK,?0?rows?affected?(6.96?sec) Records:?0??Duplicates:?0??Warnings:?0

查看該表的索引

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?????????|?????2360697?|?????NULL?|?NULL???|??????|?BTREE??????|?????????|???????????????| |?participant?|??????????1?|?index_conferenceid?|????????????1?|?conferenceid?|?A?????????|?????????199?|?????NULL?|?NULL???|?YES??|?BTREE??????|?????????|???????????????| |?participant?|??????????1?|?index_pin??????????|????????????1?|?pin??????????|?A?????????|?????????199?|?????NULL?|?NULL???|?YES??|?BTREE??????|?????????|???????????????| +-------------+------------+--------------------+--------------+--------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 3?rows?in?set?(0.00?sec)

再次查看該SQL的執行計劃，不再走全表掃描，而是走了index_merge,執行時間也大大縮短，

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志一切正常

通過此次事故：

① 及時優化慢查詢

② 打開參數?log_queries_not_using_indexes? 及時發現沒有走索引的SQL

③可以采用SQL審核-自主上線平臺，解放人力

https://blog.51cto.com/hcymysql/2053798#comment

轉載于:https://blog.51cto.com/11784929/2091555

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