[[query-dsl-missing-filter]]
=== Missing Filter

Filters documents where a specific field has no value in them.

[source,js]
--------------------------------------------------
{
    "constant_score" : {
        "filter" : {
            "missing" : { "field" : "user" }
        }
    }
}
--------------------------------------------------

By default, the filter will only find "missing" fields, i.e., fields
that have no values. It can be configured also to find fields with an
explicit `null_value` mapped for them. Here is an example that will both
find missing field that don't exists (`existence` set to `true`), or
have null values (`null_value` set to `true`).

[source,js]
--------------------------------------------------
{
    "constant_score" : {
        "filter" : {
            "missing" : { 
                "field" : "user",
                "existence" : true,
                "null_value" : true
            }
        }
    }
}
--------------------------------------------------

[float]
==== Caching

The result of the filter is always cached.
