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

{
    "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).

{
    "constant_score" : {
        "filter" : {
            "missing" : {
                "field" : "user",
                "existence" : true,
                "null_value" : true
            }
        }
    }
}

Cachingedit

The result of the filter is always cached.