OpenSearch/docs/reference/search/search-fields.asciidoc

[discrete]
[[search-fields]]
=== Return fields in a search

By default, each hit in the search response includes the document
<<mapping-source-field,`_source`>>, which is the entire JSON object that was
provided when indexing the document. If you only need certain fields in the
search response, you can use the `_source` parameter to restrict what parts of
the source are returned. This is called _source filtering_.

.*Example*
[%collapsible]
====
The following search API request sets the `_source` request body parameter to
`false`. The document source is not included in the response.

[source,console]
----
GET /_search
{
  "_source": false,
  "query": {
    "term": {
      "user.id": "8a4f500d"
    }
  }
}
----

To return only a subset of source fields, specify a wildcard (`*`) pattern in
the `_source` parameter. The following search API request returns the source for
only the `obj` field and its properties.

[source,console]
----
GET /_search
{
  "_source": "obj.*",
  "query": {
    "term": {
      "user.id": "8a4f500d"
    }
  }
}
----

You can also specify an array of wildcard patterns in the `_source` field. The
following search API request returns the source for only the `obj1` and
`obj2` fields and their properties.

[source,console]
----
GET /_search
{
  "_source": [ "obj1.*", "obj2.*" ],
  "query": {
    "term": {
      "user.id": "8a4f500d"
    }
  }
}
----

For finer control, you can specify an object containing arrays of `includes` and
`excludes` patterns in the `_source` parameter.

If the `includes` property is specified, only source fields that match one of
its patterns are returned. You can exclude fields from this subset using the
`excludes` property.

If the `includes` property is not specified, the entire document source is
returned, excluding any fields that match a pattern in the `excludes` property.

The following search API request returns the source for only the `obj1` and
`obj2` fields and their properties, excluding any child `description` fields.

[source,console]
----
GET /_search
{
  "_source": {
    "includes": [ "obj1.*", "obj2.*" ],
    "excludes": [ "*.description" ]
  },
  "query": {
    "term": {
      "user.id": "8a4f500d"
    }
  }
}
----
====

Returning fields using only the document source has some limitations:

* The `_source` field does not include <<multi-fields, multi-fields>> or
<<alias, field aliases>>. Likewise, a field in the source does not contain
values copied using the <<copy-to,`copy_to`>> mapping parameter.
* Since the `_source` is stored as a single field in Lucene, the whole source
object must be loaded and parsed, even if only a small number of fields are
needed.

{es} supports some alternative methods for returning fields that help avoid
these downsides:

* The <<request-body-search-docvalue-fields, `docvalue_fields`>>
parameter allows for loading fields from their doc values. This can be a good
choice when returning a fairly small number of fields that support doc values,
such as keywords and dates.
* It's also possible to store an individual field's values by using the
<<mapping-store,`store`>> mapping option. You can use the
<<request-body-search-stored-fields, `stored_fields`>> parameter to return
these stored values in the search response.