InnoDB automatically detects transaction
deadlocks and rolls back a
transaction or transactions to break the deadlock.
InnoDB tries to pick small transactions to
roll back, where the size of a transaction is determined by the
number of rows inserted, updated, or deleted.
InnoDB is aware of table locks if
innodb_table_locks = 1 (the default) and
autocommit = 0, and the MySQL
layer above it knows about row-level locks. Otherwise,
InnoDB cannot detect deadlocks where a table
lock set by a MySQL
statement or a lock set by a storage engine other than
InnoDB is involved. Resolve these situations
by setting the value of the
InnoDB performs a complete rollback of a
transaction, all locks set by the transaction are released.
However, if just a single SQL statement is rolled back as a
result of an error, some of the locks set by the statement may
be preserved. This happens because
stores row locks in a format such that it cannot know afterward
which lock was set by which statement.