33 lines
1.2 KiB
Plaintext
33 lines
1.2 KiB
Plaintext
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[[joining-queries]]
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== Joining queries
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Performing full SQL-style joins in a distributed system like Elasticsearch is
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prohibitively expensive. Instead, Elasticsearch offers two forms of join
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which are designed to scale horizontally.
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<<query-dsl-nested-query,`nested` query>>::
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Documents may contains fields of type <<mapping-nested-type,`nested`>>. These
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fields are used to index arrays of objects, where each object can be queried
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(with the `nested` query) as an independent document.
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<<query-dsl-has-child-query,`has_child`>> and <<query-dsl-has-parent-query,`has_parent`>> queries::
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A <<mapping-parent-field,parent-child relationship>> can exist between two
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document types within a single index. The `has_child` query returns parent
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documents whose child documents match the specified query, while the
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`has_parent` query returns child documents whose parent document matches the
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specified query.
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Also see the <<query-dsl-terms-lookup,terms-lookup mechanism>> in the `terms`
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query, which allows you to build a `terms` query from values contained in
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another document.
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include::nested-query.asciidoc[]
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include::has-child-query.asciidoc[]
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include::has-parent-query.asciidoc[]
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