死鎖分析是DBA日常工作之一，一般死鎖分析的步驟如下
- 閱讀死鎖日誌
- 查看錶機構，甚至不需要
- 定位事務場景，進行分析
而正確的理解死鎖日誌，是進行死鎖分析的重點，下面就是對死鎖日誌的分段解讀。
一般的死鎖日誌如下
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LATEST DETECTED DEADLOCK
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2019-01-09 15:11:45 0x70000cc97000 //死鎖發生時間
*** (1) TRANSACTION: //事務1
TRANSACTION 1819662/*事務id，trx->id*/, ACTIVE 13 sec starting index read //事務1從開始執行到被死鎖檢測經歷的時間，生產環境一般看到的是0
mysql tables in use 1, locked 1 //事務1當前查詢使用到的表，以及已經加鎖的表。分別是trx->n_mysql_tables_in_use，trx->mysql_n_tables_locked
LOCK WAIT 2 lock struct(s), heap size 1160, 1 row lock(s)// 這行的LOCK WAIT 2 lock struct(s),應該分成兩部分解讀，而不是說等待兩個鎖結構。LOCK WAIT表示事務狀態處於鎖等待，但是這是個不加鎖的髒讀輸出。有可能不準確，2 lock struct(s)表示此事務中的鎖結構數目，UT_LIST_GET_LEN(trx->lock.trx_locks); heap size代表內存堆的byte長度。1 row locks(s) 是鎖了一行。
MySQL thread id 5, OS thread handle 123145517932544, query id 39 localhost root statistics
select * from t2 where id = 5 for update
//processlist id , 對應的操作系統的線程結構（pthread_t），查詢ID，來源IP，用戶名，操作信息（proc_info，不受保護）
*** (1) WAITING FOR THIS LOCK TO BE GRANTED: //此事務要加的鎖，但是被阻塞。
RECORD LOCKS/*行鎖*/ space id 68/*表空間id*/ page no 3/*page id*/ n bits 72/*bitmap的大小*/ index PRIMARY /*索引*/of table `test_lock`.`t2`/*表名*/ trx id 1819662 /*事務id*/ lock_mode X /*排他鎖*/ locks rec but not gap /*只鎖行記錄，不鎖間隙*/ waiting /*加鎖等待*/
Record lock, heap no 6/*索引頁中所處的邏輯位置*/ PHYSICAL RECORD: n_fields 4; compact format; info bits 0
0: len 4; hex 80000005; asc ;;
1: len 6; hex 0000001b984f; asc O;;
2: len 7; hex 48000001890110; asc H ;;
3: len 8; hex 7570646174655f33; asc update_3;;
*** (2) TRANSACTION:
TRANSACTION 1819663, ACTIVE 24 sec starting index read
mysql tables in use 1, locked 1
4 lock struct(s), heap size 1160, 2 row lock(s)
MySQL thread id 4, OS thread handle 123145516838912, query id 40 localhost root statistics
select * from t2 where id = 5 for update
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 68 page no 3 n bits 72 index PRIMARY of table `test_lock`.`t2` trx id 1819663 lock mode S locks rec but not gap
Record lock, heap no 6 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
0: len 4; hex 80000005; asc ;;
1: len 6; hex 0000001b984f; asc O;;
2: len 7; hex 48000001890110; asc H ;;
3: len 8; hex 7570646174655f33; asc update_3;;
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 68 page no 3 n bits 72 index PRIMARY of table `test_lock`.`t2` trx id 1819663 lock_mode X locks rec but not gap waiting
Record lock, heap no 6 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
0: len 4; hex 80000005; asc ;;
1: len 6; hex 0000001b984f; asc O;;
2: len 7; hex 48000001890110; asc H ;;
3: len 8; hex 7570646174655f33; asc update_3;;
*** WE ROLL BACK TRANSACTION (1)