opensearch-docs-cn/_query-dsl/term/prefix.md

layout	title	parent	grand_parent	nav_order
default	Prefix	Term-level queries	Query DSL	40

Prefix query

Use the prefix query to search for terms that begin with a specific prefix. For example, the following query searches for documents in which the speaker field contains a term that starts with KING H:

GET shakespeare/_search
{
  "query": {
    "prefix": {
      "speaker": "KING H"
    }
  }
}

{% include copy-curl.html %}

To provide parameters, you can use a query equivalent to the preceding one with the following extended syntax:

GET shakespeare/_search
{
  "query": {
    "prefix": {
      "speaker": {
        "value": "KING H"
      }
    }
  }
}

{% include copy-curl.html %}

Parameters

The query accepts the name of the field (<field>) as a top-level parameter:

GET _search
{
  "query": {
    "prefix": {
      "<field>": {
        "value": "sample",
        ... 
      }
    }
  }
}

{% include copy-curl.html %}

The <field> accepts the following parameters. All parameters except value are optional.

Parameter	Data type	Description
value	String	The term to search for in the field specified in <field>.
case_insensitive	Boolean	If true, allows case-insensitive matching of the value with the indexed field values. Default is false (case sensitivity is determined by the field's mapping).
rewrite	String	Determines how OpenSearch rewrites and scores multi-term queries. Valid values are constant_score, scoring_boolean, constant_score_boolean, top_terms_N, top_terms_boost_N, and top_terms_blended_freqs_N. Default is constant_score.

If search.allow_expensive_queries is set to false, prefix queries are not run. If index_prefixes is enabled, the search.allow_expensive_queries setting is ignored and an optimized query is built and run. {: .important}