Mysql deadlock timeout8/11/2023 ![]() ![]() I hope that this article will help clear such misconceptions.īack to the topic of this article. Deadlocks aren’t dangerous if you retry the transaction that failed due to deadlock and follow the steps given below in this article. I still hear from some customers who are using MyISAM tables that their reason for not switching to InnoDB is the deadlock problem. Small transactions are less prone to deadlocks but it can still happen if transactions do not use the same order of operations.Ĭ) Deadlocks are dangerous. gap locking).ī) Small transactions are not affected by deadlocks. However, isolation level sets fewer locks, hence it can help you to avoid certain lock types (e.g. ![]() Isolation level changes the behavior of read operations, but deadlock occurs due to write operations. The possibility of deadlocks is not affected by isolation level. There are some misconceptions about deadlocks:Ī) Transaction isolation levels are responsible for deadlocks. By default, MySQL detects the deadlock condition and to break the deadlock it rolls back one of the transactions.įor a deadlock example, see InnoDB deadlocks Some misconceptions It is a classic problem for all databases including MySQL/PostgreSQL/Oracle etc. Deadlocks-where two or more transactions are waiting for one another to give up locks before the transactions can proceed successfully-are an unwanted situation. RECORD LOCKS space id 45178 page no 57766 n bits 576 index UNIQUE_aggregate of table `data`.MySQL has locking capabilities, for example table and row level locking, and such locks are needed to control data integrity in multi-user concurrency. *** (2) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 45178 page no 57766 n bits 576 index UNIQUE_aggregate of table `data`.`aggregate` trx id 82197992 lock_mode X locks rec but not gap Replace into aggregate SELECT date, PRODUCT_FK, DATA_POINT, LOS, SUM(`HOUR`) FROM aggregate_temp GROUP BY date, PRODUCT_FK, DATA_POINT, LOS MySQL thread id 94049, OS thread handle 8428, query id 1096943836 localhost 127.0.0.1 cpro Creating sort index ![]() Record lock, heap no 447 PHYSICAL RECORD: n_fields 5 compact format info bits 32Ģ: len 726976616c73 asc arrivals RECORD LOCKS space id 45178 page no 57766 n bits 576 index UNIQUE_aggregate of table `data`.`aggregate` trx id 82199210 lock_mode X locks rec but not gap waiting ![]() *** (1) WAITING FOR THIS LOCK TO BE GRANTED: MySQL thread id 94048, OS thread handle 13292, query id 1096831619 localhost 127.0.0.1 cpro Sending dataĭELETE aggr FROM aggregate aggr INNER JOIN product p ON aggr.product_fk=p.product_pk WHERE p.id=2 AND date BETWEEN ' 00:00:00' AND ' 23:59:59.999' LOCK WAIT 16 lock struct(s), heap size 1136, 618 row lock(s) TRANSACTION 82199210, ACTIVE 59 sec fetching rows 2nd thread tries delete record from aggregateĬan someone please help me how can I reproduce the same issue, or what causes this issue.īelow is the engine status.1st thread tries to execute query replace into aggregate from temp table.There were 2 threads running at same time. I took the InnoDB engine status to check the which query generated the deadlock, but I am not able to understand why this is generated. Yesterday on my production I got deadlock related issue for my application, ![]()
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