What is table-level locking and row-level locking in MySQL?
Table-level locking systems always lock entire tables. Row-level locking systems can lock entire tables if the WHERE clause of a statement cannot use an index. For example, UPDATES that cannot use an index lock the entire table.
How many queries can MySQL handle?
MySQL :: Wikipedia’s MySQL databases handle over 25,000 SQL queries per second.
What is row level lock?
Row-level locking means that only the row that is accessed by an application will be locked. Hence, all other rows that belong to the same page are free and can be used by other applications. The Database Engine can also lock the page on which the row that has to be locked is stored.
What happens when two threads try to lock the same rows?
When two threads (two database connections) try to lock the same rows in a different order, you might get a deadlock. For instance, transaction A wants to change row #1 and row #2. Transaction B wants to change the same rows but in a different order (row #2, then row #1).
How does row level locking work in MySQL?
MySQL uses row-level locking for InnoDB tables to support simultaneous write access by multiple sessions, making them suitable for multi-user, highly concurrent, and OLTP applications. Fewer lock conflicts when different sessions access different rows. Fewer changes for rollbacks.
What kind of locking is used in MySQL?
MySQL uses table-level locking for MyISAM, MEMORY, and MERGE tables, permitting only one session to update those tables at a time. This locking level makes these storage engines more suitable for read-only, read-mostly, or single-user applications.
What happens when two users update the same row in MySQL?
“MySQL enables client sessions to acquire table locks explicitly for the purpose of cooperating with other sessions for access to tables, or to prevent other sessions from modifying tables during periods when a session requires exclusive access to them.”