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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)
74 lines
1.9 KiB
Plaintext
74 lines
1.9 KiB
Plaintext
[[query-dsl-prefix-query]]
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=== Prefix query
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++++
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<titleabbrev>Prefix</titleabbrev>
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++++
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Returns documents that contain a specific prefix in a provided field.
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[[prefix-query-ex-request]]
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==== Example request
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The following search returns documents where the `user` field contains a term
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that begins with `ki`.
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[source,console]
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----
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GET /_search
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{
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"query": {
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"prefix": {
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"user": {
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"value": "ki"
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}
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}
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}
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}
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----
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[[prefix-query-top-level-params]]
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==== Top-level parameters for `prefix`
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`<field>`::
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(Required, object) Field you wish to search.
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[[prefix-query-field-params]]
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==== Parameters for `<field>`
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`value`::
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(Required, string) Beginning characters of terms you wish to find in the
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provided `<field>`.
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`rewrite`::
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(Optional, string) Method used to rewrite the query. For valid values and more
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information, see the <<query-dsl-multi-term-rewrite, `rewrite` parameter>>.
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[[prefix-query-notes]]
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==== Notes
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[[prefix-query-short-ex]]
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===== Short request example
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You can simplify the `prefix` query syntax by combining the `<field>` and
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`value` parameters. For example:
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[source,console]
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----
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GET /_search
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{
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"query": {
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"prefix" : { "user" : "ki" }
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}
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}
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----
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[[prefix-query-index-prefixes]]
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===== Speed up prefix queries
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You can speed up prefix queries using the <<index-prefixes,`index_prefixes`>>
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mapping parameter. If enabled, {es} indexes prefixes between 2 and 5
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characters in a separate field. This lets {es} run prefix queries more
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efficiently at the cost of a larger index.
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[[prefix-query-allow-expensive-queries]]
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===== Allow expensive queries
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Prefix queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
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is set to false. However, if <<index-prefixes, `index_prefixes`>> are enabled, an optimised query is built which
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is not considered slow, and will be executed in spite of this setting.
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