OpenSearch/docs/reference/mapping/fields/id-field.asciidoc

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[[mapping-id-field]]
=== `_id` field
Each document indexed is associated with a <<mapping-type-field,`_type`>> (see
<<all-mapping-types,Mapping Types>>) and an <<mapping-id-field,`_id`>>. The
`_id` field is not indexed as its value can be derived automatically from the
<<mapping-uid-field,`_uid`>> field.
The value of the `_id` field is accessible in queries and scripts, but _not_
in aggregations or when sorting, where the <<mapping-uid-field,`_uid`>> field
should be used instead:
[source,js]
--------------------------
# Example documents
PUT my_index/my_type/1
{
"text": "Document with ID 1"
}
PUT my_index/my_type/2
{
"text": "Document with ID 2"
}
GET my_index/_search
{
"query": {
"terms": {
"_id": [ "1", "2" ] <1>
}
},
"script_fields": {
"UID": {
"script": "doc['_id']" <2>
}
}
}
--------------------------
// AUTOSENSE
<1> Querying on the `_id` field (also see the <<query-dsl-ids-query,`ids` query>>)
<2> Accessing the `_id` field in scripts (inline scripts must be <<enable-dynamic-scripting,enabled>> for this example to work)