![]() Deadlocks generally occur if transactions try to lock resources in a different order. When multiple transactions are holding or requesting locks on the same resources creating a cycle of dependencies. The server is unaware of storage engine locks and each storage engine implements locks in different ways. Row locks are part of the storage engine, not the server. Row-level locks are available within InnoDB and Falcon storage engines, but not exclusive to. This type of lock offers the best concurrency but carries the highest overhead. ALTER TABLE will always use a table lock, regardless of which storage engine is in place. Write locks have a higher priority than read locks a request for a write lock will jump to the front of the lock queue if read locks are already queued. READ LOCAL table locks allow concurrent write operations of some sorts. When there are no write locks, clients can set read locks and, as aforementioned, don’t conflict with other client read locks. This keeps all other read and write operations in a queue. If a client wishes to write to a table (insert, delete, update), it obtains a write lock. Lock management is important in storage engine design.īasic and with the lowest overhead. Write locks are exclusive – they block read and write locks.Įach lock operation has an overhead. Many clients can read a resource simultaneously and don’t interfere with each other. Read locks on a resource are shared, mutually nonblocking. ![]()
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