elasticsearch/docs/reference/query-dsl/prefix-query.asciidoc

[[query-dsl-prefix-query]]
=== Prefix query
++++
<titleabbrev>Prefix</titleabbrev>
++++

Returns documents that contain a specific prefix in a provided field.

[[prefix-query-ex-request]]
==== Example request

The following search returns documents where the `user.id` field contains a term
that begins with `ki`.

[source,console]
----
GET /_search
{
  "query": {
    "prefix": {
      "user.id": {
        "value": "ki"
      }
    }
  }
}
----

[[prefix-query-top-level-params]]
==== Top-level parameters for `prefix`
`<field>`::
(Required, object) Field you wish to search.

[[prefix-query-field-params]]
==== Parameters for `<field>`
`value`::
(Required, string) Beginning characters of terms you wish to find in the
provided `<field>`.

`rewrite`::
(Optional, string) Method used to rewrite the query. For valid values and more
information, see the <<query-dsl-multi-term-rewrite, `rewrite` parameter>>.

`case_insensitive`::
(Optional, boolean) allows ASCII case insensitive matching of the
value with the indexed field values when set to true. Setting to false is disallowed.

[[prefix-query-notes]]
==== Notes

[[prefix-query-short-ex]]
===== Short request example
You can simplify the `prefix` query syntax by combining the `<field>` and
`value` parameters. For example:

[source,console]
----
GET /_search
{
  "query": {
    "prefix" : { "user" : "ki" }
  }
}
----

[[prefix-query-index-prefixes]]
===== Speed up prefix queries
You can speed up prefix queries using the <<index-prefixes,`index_prefixes`>>
mapping parameter. If enabled, {es} indexes prefixes between 2 and 5
characters in a separate field. This lets {es} run prefix queries more
efficiently at the cost of a larger index.

[[prefix-query-allow-expensive-queries]]
===== Allow expensive queries
Prefix queries will not be executed if <<query-dsl-allow-expensive-queries, `search.allow_expensive_queries`>>
is set to false. However, if <<index-prefixes, `index_prefixes`>> are enabled, an optimised query is built which
is not considered slow, and will be executed in spite of this setting.