70 lines
1.9 KiB
Markdown
70 lines
1.9 KiB
Markdown
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---
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layout: default
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title: Prefix
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parent: Term-level queries
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grand_parent: Query DSL
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nav_order: 40
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---
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# Prefix query
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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`:
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```json
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GET shakespeare/_search
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{
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"query": {
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"prefix": {
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"speaker": "KING H"
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}
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}
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}
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```
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{% include copy-curl.html %}
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To provide parameters, you can use a query equivalent to the preceding one with the following extended syntax:
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```json
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GET shakespeare/_search
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{
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"query": {
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"prefix": {
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"speaker": {
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"value": "KING H"
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}
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}
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}
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}
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```
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{% include copy-curl.html %}
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## Parameters
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The query accepts the name of the field (`<field>`) as a top-level parameter:
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```json
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GET _search
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{
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"query": {
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"prefix": {
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"<field>": {
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"value": "sample",
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...
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}
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}
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}
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}
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```
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{% include copy-curl.html %}
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The `<field>` accepts the following parameters. All parameters except `value` are optional.
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Parameter | Data type | Description
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:--- | :--- | :---
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`value` | String | The term to search for in the field specified in `<field>`.
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`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).
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`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`.
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If [`search.allow_expensive_queries`]({{site.url}}{{site.baseurl}}/query-dsl/index/#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.
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{: .important}
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