I went through MySQL logs and found the reason for deadlock
1st thread is trying to execute below query. Which is waiting for thread 2.
UPDATE M_SAMP SET MM_Q_IND=0 WHERE M_ID IN (SELECT M_ID FROM MM_RVW_SAMP WHERE TARGET_M_ID IN(19))
The result of inner query (SELECT M_ID FROM MM_RVW_SAMP WHERE TARGET_M_ID IN(19)
) is M_ID = 3562
.
2nd thread is executing below query.
DELETE FROM M_SAMP WHERE M_ID=3455
There is no foreign key
relation defined in M_SAMP and MM_RVW_SAMP tables. And M_ID is primary key of M_SAMP table. And engine is InnoDB
. And this issue is repeating.
Can any one help me, how locks are granted because of which deadlock is happening?
Logs
------------------------
LATEST DETECTED DEADLOCK
------------------------
2015-02-23 10:52:28 de8
*** (1) TRANSACTION:
TRANSACTION 13275344, ACTIVE 0 sec fetching rows
mysql tables in use 2, locked 2
LOCK WAIT 25 lock struct(s), heap size 2408, 1394 row lock(s), undo log entries 1
MySQL thread id 1455, OS thread handle 0x11ac, query id 39660 xyz 192.168.1.108 userName Sending data
UPDATE M_SAMP SET FLAG=0 WHERE M_ID IN (SELECT M_ID FROM MM_RVW_SAMP WHERE TARGET_M_ID IN(19))
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 61569 page no 65 n bits 176 index `PRIMARY` of table `dbName`.`m_samp` trx id 13275344 lock_mode X waiting
Record lock, heap no 3 PHYSICAL RECORD: n_fields 29; compact format; info bits 0
*** (2) TRANSACTION:
TRANSACTION 13275335, ACTIVE 0 sec starting index read
mysql tables in use 1, locked 1
254 lock struct(s), heap size 27512, 21595 row lock(s), undo log entries 7
MySQL thread id 1458, OS thread handle 0xde8, query id 39664 xyz 192.168.1.108 userName updating
DELETE FROM M_SAMP WHERE M_ID=3455
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 61569 page no 65 n bits 176 index `PRIMARY` of table `dbName`.`m_samp` trx id 13275335 lock mode S locks rec but not gap
Record lock, heap no 3 PHYSICAL RECORD: n_fields 29; compact format; info bits 0
Thank you.
Update:
Number of records in M_SAMP
table is 3524
and in MM_RVW_SAMP
is 2
.
Below is the result of EXPLAIN
query.
EXPLAIN UPDATE M_SAMP SET MM_Q_IND=1 WHERE M_ID IN (SELECT M_ID FROM MM_RVW_SAMP WHERE TARGET_M_ID IN(19))
SHOW CREATE TABLE
) and yourGLOBAL transaction-isolation
value.tx_isolation
isREPEATABLE-READ
5.6.16
EXPLAIN
the first query, maybe it is still doing the scan. In that case, setting the mode READ-COMMITTED or doing a JOIN would also fix the issue.