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In a SQL database, a record is typically called a "row". The introduction of granular (subset) locks creates the possibility for a situation called deadlock. Deadlock is possible when incremental locking (locking one entity, then locking one or more additional entities) is used. To illustrate, if two bank customers asked two clerks to obtain ...
Archive differs from the other MySQL analytical engine, MyISAM, by being a row-level locking engine and by keeping a constant version snapshot throughout a single query (making it MVCC). This means that Archive does not lock for concurrent bulk inserts. For bulk inserts it performs an interlaced INSERT, so unlike MyISAM, order is not guaranteed.
Determining what level of granularity to use for locking is done by locking the finest level possible (i.e., at the lowest leaf), and then escalating these locks to higher levels in the file hierarchy to cover more records or file elements as needed in a process known as "lock escalation".
Yes (Row-level locking) Yes Yes API & GUI & SQL: Yes Advantage Database Server: Yes Yes ... MySQL databases are analogous in function to PostgreSQL-schemas, insomuch ...
Isolation is typically enforced at the database level. However, various client-side systems can also be used. It can be controlled in application frameworks or runtime containers such as J2EE Entity Beans [2] On older systems, it may be implemented systemically (by the application developers), for example through the use of temporary tables.
(Do not confuse this technique with row-level versioning used for optimistic locking. For optimistic locking each row has an independent version number, typically a sequential counter. This allows a process to atomically update a row and increment its counter only if another process has not incremented the counter. But CDC cannot use row-level ...
Row level triggers would execute once for each row that is affected by the UPDATE. It is important to keep in mind if no rows are affected by the UPDATE command, the trigger will not execute any code within the trigger. Statement level triggers will be called once regardless of how many rows are affected by the UPDATE. Here it is important to ...
In databases and transaction processing, two-phase locking (2PL) is a pessimistic concurrency control method that guarantees conflict-serializability. [ 1 ] [ 2 ] It is also the name of the resulting set of database transaction schedules (histories).