![]() Not sure what happens exactly in your case, but maybe it helps. If table lock happen, the lock contention is higher and the likelihood of deadlock increases. Be sure then to always have index on the foreign keys (and of course primary keys), otherwise it could result in a table lock instead of a row lock. It might result in other lock being acquired than the row that is modified. To do so, the database needs to check the foreign keys in the related tables. The first transaction is typically pretty fast when it doesnt hit a deadlock (0.1 - 0.2 seconds to complete), but it does seem to hit deadlocks about 10 of the time. The way to resolve this is to use ORDER BY to ensure rows are always locked in the same order. In a typical 5 minutes, the queue will build up a backlog of about 100 items, though occasionally it can be in the thousands if a lot of changes have occurred in the catalog. Transaction 2: Attempts to lock row A and deadlocks. When a row in inserted/update/delete, the database need to check the relational constraints, that is, make sure the relations are consistent. Transaction 1: Attempts to lock row B and blocks. Are you doing something else in the transaction?Ī deadlock can however happen if there are missing indexes. always table A first, then table B).īut if within one transaction you insert in only one table this condition is met, and this should then usually not lead to a deadlock. Fortunately, MySQL (using the InnoDB engine) offers an extremely simple way to diagnose deadlocks, assuming you know where to look. Generally speaking, to avoid deadlock you must acquire lock always in the same order even in different transaction (e.g. A deadlock in MySQL happens when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. ![]() Deadlocks being present do not always indicate an issue but often. To avoid deadlock, you must then make sure that concurrent transactions don't update row in an order that could result in a deadlock. Deadlocks in MySQL occur when two or more transactions mutually hold and request for locks. To my understanding, a select does not acquire lock and should not be the cause of the deadlock.Įach time you insert/update/or delete a row, a lock is acquired. ![]()
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