[[query-dsl-nested-filter]]
=== Nested Filter

A `nested` filter works in a similar fashion to the
<<query-dsl-nested-query,nested>> query, except it's
used as a filter. It follows exactly the same structure, but also allows
to cache the results (set `_cache` to `true`), and have it named (set
the `_name` value). For example:

[source,js]
--------------------------------------------------
{
    "filtered" : {
        "query" : { "match_all" : {} },
        "filter" : {
            "nested" : {
                "path" : "obj1",
                "filter" : {
                    "bool" : {
                        "must" : [
                            {
                                "term" : {"obj1.name" : "blue"}
                            },
                            {
                                "range" : {"obj1.count" : {"gt" : 5}}
                            }
                        ]
                    }
                },
                "_cache" : true
            }
        }
    }
}
--------------------------------------------------

[float]
==== Join option

The nested filter also supports a `join` option which controls whether to perform the block join or not.
By default, it's enabled. But when it's disabled, it emits the hidden nested documents as hits instead of the joined root document.

This is useful when a `nested` filter is used in a facet where nested is enabled, like you can see in the example below:

[source,js]
--------------------------------------------------
{
    "query" : {
        "nested" : {
            "path" : "offers",
            "query" : {
                "match" : {
                    "offers.color" : "blue"
                }
            }
        }
    },
    "facets" : {
        "size" : {
            "terms" : {
                "field" : "offers.size"
            },
            "facet_filter" : {
                "nested" : {
                    "path" : "offers",
                    "query" : {
                        "match" : {
                            "offers.color" : "blue"
                        }
                    },
                    "join" : false
                }
            },
            "nested" : "offers"
        }
    }
}'
--------------------------------------------------
