OpenSearch/docs/reference/query-dsl/exists-query.asciidoc

[[query-dsl-exists-query]]
=== Exists Query

Returns documents that have at least one non-`null` value in the original field:

[source,js]
--------------------------------------------------
GET /_search
{
    "query": {
        "exists" : { "field" : "user" }
    }
}
--------------------------------------------------
// CONSOLE

For instance, these documents would all match the above query:

[source,js]
--------------------------------------------------
{ "user": "jane" }
{ "user": "" } <1>
{ "user": "-" } <2>
{ "user": ["jane"] }
{ "user": ["jane", null ] } <3>
--------------------------------------------------
// NOTCONSOLE
<1> An empty string is a non-`null` value.
<2> Even though the `standard` analyzer would emit zero tokens, the original field is non-`null`.
<3> At least one non-`null` value is required.

These documents would *not* match the above query:

[source,js]
--------------------------------------------------
{ "user": null }
{ "user": [] } <1>
{ "user": [null] } <2>
{ "foo":  "bar" } <3>
--------------------------------------------------
// NOTCONSOLE
<1> This field has no values.
<2> At least one non-`null` value is required.
<3> The `user` field is missing completely.

[float]
==== `null_value` mapping

If the field mapping includes the <<null-value,`null_value`>> setting
then explicit `null` values are replaced with the specified `null_value`.  For
instance, if the `user` field were mapped as follows:

[source,js]
--------------------------------------------------
PUT /example?include_type_name=true
{
  "mappings": {
    "_doc": {
      "properties": {
        "user": {
          "type": "keyword",
          "null_value": "_null_"
        }
      }
    }
  }
}
--------------------------------------------------
// CONSOLE

then explicit `null` values would be indexed as the string `_null_`, and the
following docs would match the `exists` filter:

[source,js]
--------------------------------------------------
{ "user": null }
{ "user": [null] }
--------------------------------------------------
// NOTCONSOLE

However, these docs--without explicit `null` values--would still have
no values in the `user` field and thus would not match the `exists` filter:

[source,js]
--------------------------------------------------
{ "user": [] }
{ "foo": "bar" }
--------------------------------------------------
// NOTCONSOLE

==== `missing` query

There isn't a `missing` query. Instead use the `exists` query inside a
`must_not` clause as follows:

[source,js]
--------------------------------------------------
GET /_search
{
    "query": {
        "bool": {
            "must_not": {
                "exists": {
                    "field": "user"
                }
            }
        }
    }
}
--------------------------------------------------
// CONSOLE

This query returns documents that have no value in the user field.