Adatbázisindexelés

Adatbázisindexelés (Database Indexing) is a data structure technique used to improve the speed of data retrieval operations on a database table. An index is a data structure, most commonly a B-tree, that stores a small portion of the table's data in a sorted order, along with pointers to the original data rows. When a query is executed, the database system can use the index to quickly locate the desired rows without having to scan the entire table. This is analogous to the index in a book, which allows you to find specific topics without reading every page.

Creating indexes can significantly speed up SELECT queries, especially on large tables where filtering or sorting is involved. However, indexes also have a cost. They consume disk space and can slow down data modification operations such as INSERT, UPDATE, and DELETE, as the index also needs to be updated along with the table data. Therefore, it is important to carefully consider which columns to index and to avoid over-indexing.

Common types of indexes include B-tree indexes, hash indexes, and full-text indexes. B-tree indexes are the most common and are suitable for a wide range of queries, including range queries and exact matches. Hash indexes are very efficient for exact match lookups but are not suitable for range queries. Full-text indexes are designed for searching within text data. The choice of index type depends on the specific query patterns and data characteristics. Proper indexing is a crucial aspect of database performance tuning.