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Joining queries
editJoining queries
editPerforming full SQL-style joins in a distributed system like Elasticsearch is prohibitively expensive. Instead, Elasticsearch offers two forms of join which are designed to scale horizontally.
-
nestedquery -
Documents may contain fields of type
nested. These fields are used to index arrays of objects, where each object can be queried (with thenestedquery) as an independent document. -
has_childandhas_parentqueries -
A parent-child relationship can exist between two
document types within a single index. The
has_childquery returns parent documents whose child documents match the specified query, while thehas_parentquery returns child documents whose parent document matches the specified query.
Also see the terms-lookup mechanism in the terms
query, which allows you to build a terms query from values contained in
another document.