Joining queries
Performing 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
joinfield relationship can exist between documents within a single index. Thehas_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 theterms-lookup mechanism in theterms query, which allows you to build aterms query from values contained in another document.
Joining queries will not be executed ifsearch.allow_expensive_queries is set to false.