Currently it is very difficult and inefficient to write a query like:

where parent has at least 5 matching children

The only way to do it is to:

• use a has_child query with an inner constant_score and score_mode of sum
• wrap in a function_score that resets the _score to zero if the min count is not achieved
• do similar score calculations for all other clauses in the query
• apply a min_score parameter to the overall query

It would be much more efficient to be able to say:

{
  "has_child": {
    "type": "foo",
    "minimum_should_match": 5,
    "query": {...some query...}
  }
}

Hopefully this could be applied to filters as well as queries?

/cc @martijnvg