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dac720d7a1
Add a new cluster setting `search.allow_expensive_queries` which by default is `true`. If set to `false`, certain queries that have usually slow performance cannot be executed and an error message is returned. - Queries that need to do linear scans to identify matches: - Script queries - Queries that have a high up-front cost: - Fuzzy queries - Regexp queries - Prefix queries (without index_prefixes enabled - Wildcard queries - Range queries on text and keyword fields - Joining queries - HasParent queries - HasChild queries - ParentId queries - Nested queries - Queries on deprecated 6.x geo shapes (using PrefixTree implementation) - Queries that may have a high per-document cost: - Script score queries - Percolate queries Closes: #29050 (cherry picked from commit a8b39ed842c7770bd9275958c9f747502fd9a3ea)
36 lines
1.3 KiB
Plaintext
36 lines
1.3 KiB
Plaintext
[[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 contain fields of type <<nested,`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 <<parent-join,`join` field relationship>> can exist between
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documents 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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include::parent-id-query.asciidoc[]
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=== Notes
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==== Allow expensive queries
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Joining queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
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is set to false.
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