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A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time said table is accessed. Indexes can be ...
Index data are system data distinct from user data, and consist primarily of pointers. Changes in a database (by insert, delete, or modify operations), may require indexes to be updated to maintain accurate user data accesses. [1] Index locking is a technique used to maintain index integrity. A portion of an index is locked during a database ...
In Computer Science, in the field of databases, non-lock concurrency control is a concurrency control method used in relational databases without using locking. There are several non-lock concurrency control methods, which involve the use of timestamps on transaction to determine transaction priority: Optimistic concurrency control
For each index, it grabs that index's primary key value from the item, then performs the same write on that index without log propagation. If the operation is an Update to a preexisting item, the updated attribute may serve as a primary key for an index, and thus the B tree for that index must update as well.
Record locking is the technique of preventing simultaneous access to data in a database, to prevent inconsistent results. The classic example is demonstrated by two bank clerks attempting to update the same bank account for two different transactions. Clerks 1 and 2 both retrieve (i.e., copy) the account's record. Clerk 1 applies and saves a ...
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.
Even though this technique is a non-locking one, in as much as the object is not locked from concurrent access for the duration of a transaction, the act of recording each timestamp against the Object requires an extremely short duration lock on the Object or its proxy.
(Singly) linked lists are fundamental data structures that are widely used as is, or to build other data structures. They consist of "nodes", or "links", that are put in some order indicated by a "next" pointer on each node. The last node in the list (the "tail") has a nil next pointer.