![]() ![]() You can read more information about deadlock at. If it was not a cycle, the second transaction would indeed wait up to innodblockwaittimeout seconds. It is important to create good indexes so that your queries do not scan more rows than necessary. a dependency is detected and InnoDB kills the most recent one to prevent an infinite loop (deadlock) They cannot just wait, because otherwise it would be an infinite wait (as they depend on each other). Also, because in this case the higher MySQL layer does not know about row-level. If you have no indexes suitable for your statement and MySQL must scan the entire table to process the statement, every row of the table becomes locked, which in turn blocks all inserts by other users to the table. Otherwise, InnoDB's automatic deadlock detection cannot detect deadlocks where such table locks are involved. To avoid the deadlock, you should set the same table locking order for both connections, for example: InnoDB is aware of table locks if innodbtablelocks 1 (the default) and autocommit 0, and the MySQL layer above InnoDB knows about row-level locks. For example, if you have a query that only needs x, then the INDEX would be preferable to the seeming equivalent PK. It is, however, debatable whether PRIMARY KEY (x), INDEX (x) is really redundant. To solve the problem, you should reorganize the application logic, in order to avoid a deadlock.Ī deadlock occurs when two parallel connections attempt to lock 2 tables in a different order, for example:Ĭonnection1 attempts to lock tableB - waits for connection2 to unlock tableB Ĭonnection2 attempts to lock tableA - waits for connection1 to unlock tableA.Īs a result, we get a deadlock. 1 There has been some talk about disallowing any truly redundant indexes. The more workers are running the more often I see a deadlock I often read an application has to expect deadlocks and should simply re-issue queries that cause a deadlock but this didn't bring any results for me. For example, if your code causes uniqueness violation, the application will get stuck. It seems the query to claim jobs and the query to update the sent column by one conflict each other causing a deadlock. This can cause performance issues and may even result in a database crash. : Deadlock found when trying to get lock try restarting transaction at .executeBatchSerially (PreparedStatement.java:1684) at .executeBatch (PreparedStatement.java:1108) at. ![]() Your code for restarting transaction on error cannot solve the problem, since re-execution of one and the same code will cause the same errors. Without intervention, deadlocks become very long running queries and in some storage engines, the query ceases to execute.
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