[ElasticSearch] Insert 6 records and query for a single record with facets: Failure when the number of records is greater than the shard size

gistfile1.sh

# Create an index:
#
curl -XDELETE 'http://127.0.0.1:9200/articles'
curl -XPUT 'http://127.0.0.1:9200/articles'

# Insert the action mapping, as a child of articles:
#
curl -XPUT 'http://127.0.0.1:9200/articles/article/_mapping' -d '
{
  "article": {
    "properties": {
      "title": {
        "store": true,
        "type": "string"
      },
      "actions": {
        "type": "nested",
        "properties": {
          "action": {
            "store": true,
            "type": "string"
          },
          "updated": {
            "store": true,
            "type": "integer"
          },
          "date": {
            "store": true,
            "format": "dateOptionalTime",
            "type": "date"
          }
        }
      }
    }
  }
}
'

# Insert some articles:
#
for ((i=1; i<7; i++))
do
  curl -XPUT 'http://127.0.0.1:9200/articles/article/'$i -d '
  {
    "title": "Article '$i'",
    "actions": [
      {"date": "2010-11-18", "updated": 1, "action": "updated"}
    ]
  }
  '
done

# Ensure the index is up-to-date:
#
curl -XPOST 'http://127.0.0.1:9200/articles/_refresh'


# Now search for some articles that have actions that took place
# on the 18th of November, 2010. Create facets for those actions:
#
curl -XGET 'http://127.0.0.1:9200/articles/_search?pretty=true' -d '
{
    "query": {
        "bool": {
            "must": [
                { "query_string": {"query": "title:\"Article 1\""} },
                {
                    "nested": {
                        "path": "actions",
                        "score_mode": "avg",
                        "_scope": "actions",
                        "query": {
                            "bool": {
                                "must": [
                                    {
                                        "range": {
                                            "actions.date": {
                                                "from": "2010-11-18",
                                                "to": "2010-11-18"
                                            }
                                        }
                                    }
                                ]
                            }
                        }
                    }
                }
            ]
        }
    },
    "facets": {
        "updated_facet": {
            "date_histogram": {
                "interval": "day",
                "key_field": "actions.date",
                "value_field": "actions.updated"
            },
            "scope": "actions"
        }
    },
    "from": 0,
    "size": 0
}'

A successful result would be for the updated facet to be set to 1, since there is only one record that matches the search criteria:

{
  "took" : 5,
  "timed_out" : false,
  "_shards" : {
    "total" : 6,
    "successful" : 6,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 1.5652475,
    "hits" : [ ]
  },
  "facets" : {
    "updated_facet" : {
      "_type" : "date_histogram",
      "entries" : [ {
        "time" : 1290038400000,
        "count" : 1,
        "min" : 1.0,
        "max" : 1.0,
        "total" : 1.0,
        "total_count" : 1,
        "mean" : 1.0
      } ]
    }
  }
}

However, if the number of shards is 5, the query returns a count of 2 instead of 1. If the number of shards is 6 then the Gist above will give a correct result, but if we change it so that it inserts 7 records instead of 6, then we're back to having a count of 2 (note also that the number of hits remains at 1, since only one article matches):

{
  "took" : 4,
  "timed_out" : false,
  "_shards" : {
    "total" : 6,
    "successful" : 6,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 2.0843315,
    "hits" : [ ]
  },
  "facets" : {
    "updated_facet" : {
      "_type" : "date_histogram",
      "entries" : [ {
        "time" : 1290038400000,
        "count" : 2,
        "min" : 1.0,
        "max" : 1.0,
        "total" : 2.0,
        "total_count" : 2,
        "mean" : 1.0
      } ]
    }
  }
}