Allow post_filter access to the _score value

Elastic Stack Elasticsearch
1

I found it's allowed to access _score inside the aggs, but not allowed to access this field in the post_filter queries, though it's executed after the aggs. Is there a reason for that it's not accessible or it could be added in the Elasticsearch in the future versions?

An example query:

{
  "body": {
    "post_filter": {
      "script": {
        "script": "_score > 100 && _score < 200"
      }
    },
    "query": {
      "function_score": {
        "functions": [{
          "script_score": {
            "script": "doc['price'].value * 100"
          }
        }]
      }
    }
  },
  "index": ["items"],
  "type": []
}

script_score could be much more complex, it's just an example.

Please comment also here on the github issue: https://github.com/elastic/elasticsearch/issues/20131

Related problem to this issue: http://stackoverflow.com/questions/39109511/how-to-filter-by-script-field-in-elasticsearch?noredirect=1&lq=1