Elasticsearch: has_child query with children aggregation - bucket counts are wrong

Question

I'm attempting to find parents based on matches in their children and retrieve children term aggregations for the matches. For some reason, the bucket count for the children aggregation is showing a higher count than actual results (I would be happy if it showed the count of the parents - or the children - in the particular children bucket).

The query is similar to the following (NOTE: I use the filtered query as I will later add a filter in addition to the query):

{
"query" : {
    "filtered" : {
        "query" : {
            "has_child" : {
            "type" : "blog_tag",
            "query" : {
                "filtered" : {
                    "query" : {
                        "term" : {
                            "tag" : "something"
                        }
                    }
                }
            }
        }
    }
},
"aggs" : {
    "my_children" : {
        "children" : {
            "type" : "my_child_type"
        },
        "aggs" : {
            "field_name" : {
                "terms" : {
                    "field" : { "blog.blog_tag.field_name" }
                }
            }
        }
    }
}     

}

What is the correct way to do this?

Answer 1

The problem was as noted in the comments. The solution was to filter the aggregation with the query,

"query" : {
    "filtered" : {
        "query" : {
            "has_child" : {
            "type" : "blog_tag",
            "query" : {
                "filtered" : {
                    "query" : {
                        "term" : {
                            "tag" : "something"
                        }
                    }
                }
            }
        }
    }
},
"aggs" : {
    "my_children" : {
        "children" : {
            "type" : "my_child_type"
        },
        "aggs" : {
            "results" : {
                "filter" : {
                    "query" : {
                        "filtered" : {
                            "query" : {
                                "term" : {
                                    "tag" : "something"
                                }
                            }
                        }
                    }
                },
                "aggs" : {
                    "field_name" : {
                        "terms" : {
                            "field" : { "blog.blog_tag.field_name" }
                       }
                    }
                }
            }
        }
    }
}