[[query-dsl-has-parent-filter]]
=== Has Parent Filter

The `has_parent` filter accepts a query and a parent type. The query is
executed in the parent document space, which is specified by the parent
type. This filter return child documents which associated parents have
matched. For the rest `has_parent` filter has the same options and works
in the same manner as the `has_child` filter.

[float]
==== Filter example

[source,js]
--------------------------------------------------
{
    "has_parent" : {
        "parent_type" : "blog",
        "query" : {
            "term" : {
                "tag" : "something"
            }
        }
    }
}  
--------------------------------------------------

The `parent_type` field name can also be abbreviated to `type`.

The way that the filter is implemented is by first running the parent
query, doing the matching up to the child doc for each document matched.

The `has_parent` filter also accepts a filter instead of a query:

[source,js]
--------------------------------------------------
{
    "has_parent" : {
        "type" : "blog",
        "filter" : {
            "term" : {
                "text" : "bonsai three"
            }
        }
    }
}    
--------------------------------------------------

[float]
==== Memory considerations

With the current implementation, all `_id` values are loaded to memory
(heap) in order to support fast lookups, so make sure there is enough
memory for it.

[float]
==== Caching

The `has_parent` filter cannot be cached in the filter cache. The `_cache`
and `_cache_key` options are a no-op in this filter. Also any filter that
wraps the `has_parent` filter either directly or indirectly will not be cached.