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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.
A large database index would typically use B-tree algorithms. BRIN is not always a substitute for B-tree, it is an improvement on sequential scanning of an index, with particular (and potentially large) advantages when the index meets particular conditions for being ordered and for the search target to be a narrow set of these values.
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 database management systems, a reverse key index strategy reverses the key value before entering it in the index. [1] E.g., the value 24538 becomes 83542 in the index. Reversing the key value is particularly useful for indexing data such as sequence numbers , where each new key value is greater than the prior value, i.e., values ...
Soundex is the most widely known of all phonetic algorithms (in part because it is a standard feature of popular database software such as IBM Db2, PostgreSQL, [2] MySQL, [3] SQLite, [4] Ingres, MS SQL Server, [5] Oracle, [6] ClickHouse, [7] Snowflake [8] and SAP ASE. [9]) Improvements to Soundex are the basis for many modern phonetic algorithms.
A database shard, or simply a shard, is a horizontal partition of data in a database or search engine. Each shard may be held on a separate database server instance, to spread load. Some data within a database remains present in all shards, [a] but some appear only in a single shard. Each shard (or server) acts as the single source for this ...
In databases, a partial index, also known as filtered index is an index which has some condition applied to it so that it includes a subset of rows in the table.. This allows the index to remain small, even though the table may be rather large, and have extreme selectivity.
An indexing algorithm that allows both sequential and keyed access to data. [3] Most databases use some variation of the B-tree for this purpose, although the original IBM ISAM and VSAM implementations did not do so. Most generally, any index for a database. Indexes are used by almost all databases.