Filterquery

Filterquery is a concept in data retrieval and processing that refers to a query designed to restrict a collection to items that meet specified conditions. It expresses predicates on one or more fields and combines them with logical operators such as and, or, and not. Filterqueries are used across databases, search engines, APIs, and data processing pipelines to return only relevant results.

In practice, filterqueries appear in different query languages and formats. They may be expressed as SQL WHERE clauses, as documents in a MongoDB find filter, as an Elasticsearch query DSL object, or as REST API query parameters. Typical predicates include equality, inequality, ranges, existence, and pattern matching.

Examples illustrate the idea. SQL: SELECT * FROM products WHERE price > 100 AND in_stock = true. MongoDB: db.products.find({ price: { $gt: 100 }, in_stock: true }). REST: GET /products?price_gt=100&in_stock=true.

Performance and security considerations are important. Filters are usually evaluated during data retrieval, so appropriate indexes and query planning are essential for efficiency. Validation and escaping help prevent injection attacks when filters are constructed from user input. In some systems, filtering can be performed client-side or server-side, or as part of a filtering pipeline that combines multiple sources.

See also: query language, predicate, data filtering, search, and data retrieval.