I've created an application which gathers prices and stores it in a database. The application runs with two threads. But now and then a deadlock occurs. I think it is because the treads insert a bulk of prices to the same table.
The table
[tripid | date | duration | price | garant | updatetime | persons | accommodationid]
The indexes
unique (tripid, date, duration, price, persons)
foreign key 'accommodationid' to table 'accommodation.id'
The query
insert into prices (tripid, date, duration, price, persons, accomodationid)
values ( 1 , 2016-6-4, 8, 200,2,32),
... a whole lot more ...
( 1 , 2016-7-4, 8, 200,2,32)
on duplicate key update price = values(price);
Becouse there can be 1000 values to insert in 1 query it takes some time. I think the deadlock occurs when the second thread wants to insert another 1000 values but the first one is not completed.
The innodb status
------------------------
LATEST DETECTED DEADLOCK
------------------------
2016-03-16 23:13:13 0xef8
*** (1) TRANSACTION:
TRANSACTION 3732195928, ACTIVE 0 sec inserting
mysql tables in use 1, locked 1
LOCK WAIT 5 lock struct(s), heap size 1136, 3 row lock(s), undo log entries 1
MySQL thread id 415, OS thread handle 7328, query id 10956855 ---(ip)-- --name-- update
insert into `prices` (tripid,`date`,`duration`,`price`,`garant`,`updatetime`,`persons`,`accommodationid`) values
(179881,'2016-03-18',2,206,'0','2016-03-16','1','119'),(179881,'2016-03-18',3,260,'0','2016-03-16','1','119'),(179881,'2016-03-18',4,313,'0','2016-03-16','1','119'),(179881,'2016-03-18',5,366,'0','2016-03-16','1','119'),(179881,'2016-03-19',2,206,'0','2016-03-16','1','119'),(179881,'2016-03-19',3,260,'0','2016-03-16','1','119'),(179881,'2016-03-19',4,313,'0','2016-03-16','1','119'),(179881,'2016-03-19',5,366,'0','2016-03-16','1','119'),(179881,'2016-03-20',2,206,'0','2016-03-16','1','119'),(179881,'2016-03-20',3,260,'0','2016-03-16','1','119'),(179881,'2016-03-20',4,313,'0','2016-03-16','1','119'),(179881,'2016-03-20',5,366,'0','2016-03-16','1','119'),(179881,'2016-03-21',2,206,'0','2016-03-16','1','119'),(179881,'2016-03-21',3,260,'0','2016-03-16','1','119'),(179881,'2016-03-21',4,313,
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 247 page no 1457 n bits 136 index keyGroup of table `travel`.`prices` trx id 3732195928 lock_mode X insert intention waiting
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
*** (2) TRANSACTION:
TRANSACTION 3732195927, ACTIVE 0 sec inserting, thread declared inside InnoDB 4529
mysql tables in use 1, locked 1
15 lock struct(s), heap size 1136, 476 row lock(s), undo log entries 472
MySQL thread id 414, OS thread handle 3832, query id 10956852 ---(ip)-- --name-- update
insert into `prices` (tripid,`date`,`duration`,`price`,`garant`,`updatetime`,`persons`,`accommodationid`) values
(179880,'2016-03-18',2,185,'0','2016-03-16','1','1438'),(179880,'2016-03-18',3,217,'0','2016-03-16','1','1438'),(179880,'2016-03-18',4,249,'0','2016-03-16','1','1438'),(179880,'2016-03-18',5,279,'0','2016-03-16','1','1438'),(179880,'2016-03-18',6,312,'0','2016-03-16','1','1438'),(179880,'2016-03-18',7,343,'0','2016-03-16','1','1438'),(179880,'2016-03-18',8,375,'0','2016-03-16','1','1438'),(179880,'2016-03-19',2,185,'0','2016-03-16','1','1438'),(179880,'2016-03-19',3,217,'0','2016-03-16','1','1438'),(179880,'2016-03-19',4,249,'0','2016-03-16','1','1438'),(179880,'2016-03-19',5,279,'0','2016-03-16','1','1438'),(179880,'2016-03-19',6,312,'0','2016-03-16','1','1438'),(179880,'2016-03-19',7,343,'0','2016-03-16','1','1438'),(179880,'2016-03-20',2,185,'0','2016-03-16','1','1438'),(179880,'2016
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 247 page no 1457 n bits 72 index keyGroup of table `travel`.`prices` trx id 3732195927 lock_mode X
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 247 page no 1457 n bits 136 index keyGroup of table `travel`.`prices` trx id 3732195927 lock_mode X insert intention waiting
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
0: len 8; hex 73757072656d756d; asc supremum;;
*** WE ROLL BACK TRANSACTION (1)
------------
The Question
How do I avoid the deadlock?
I seem to have fixed it by first locking the table, then do the huge query and unlock it so the second thread gets acces.
LOCK TABLES prices WRITE;
insert into prices (tripid, date, duration, price, persons, accomodationid)
values ( 1 , 2016-6-4, 8, 200,2,32),
... a whole lot more ...
( 1 , 2016-7-4, 8, 200,2,32)
on duplicate key update price = values(price);
UNLOCK TABLES;