collectionindexes

Collectionindexes refer to data structures and mechanisms used to improve access to elements within a collection by providing fast lookup, ordering, and range queries. They function by maintaining a separate data structure that maps keys or attributes to positions or references in the primary collection. They are common in databases for tables and document stores, as well as in in-memory collections in programming languages.

Common index types include hash indexes for exact-match lookups; tree-based indexes such as B-tree and B+-tree for range queries and ordered access; multikey indexes for fields with multiple values; composite indexes on multiple attributes; unique indexes that enforce uniqueness; and full-text indexes for textual search.

Construction and maintenance involve creating an index on a collection, either by building it from existing data or declaring it ahead of time. Indices require maintenance on insertions, updates, and deletions to keep them synchronized with the primary collection. They typically improve read performance at the cost of additional write overhead and storage usage. The decision to use an index depends on access patterns, query workload, and data cardinality.

Scope and examples vary by system. In relational databases, indexes speed up SELECT queries with WHERE clauses on indexed columns. In document stores, indexes are created on fields used in queries to accelerate lookups. In programming language libraries, maps and sorted containers perform similar functions by providing fast key-based retrieval and ordered iteration.

See also: indexing, database index, B-tree, hash table, data structure.