Filters documents that have fields containing terms with a specified prefix (not analyzed). Similar to phrase query, except that it acts as a filter. Can be placed within queries that accept a filter.

{
    "constant_score" : {
        "filter" : {
            "prefix" : { "user" : "ki" }
        }
    }
}

Caching

The result of the filter is cached by default. The `_cache` can be set to `false` in order not to cache it. Here is an example:

{
    "constant_score" : {
        "filter" : {
            "prefix" : { 
                "user" : "ki",
                "_cache" : false
            }
        }
    }
}