date range filter improvement

gistfile1.txt

time curl "localhost:9200/stats-2016.01.05/nextgen-stats/_search?pretty" -d '{
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      },
      "filter": {
        "bool": {
          "must": [
            {
              "range": {
                "@timestamp": {
                  "gte": "now-12h/h",
                  "lte": "now"
                }
              }
            }
          ],
          "must_not": []
        }
      }
    }
  },
  "size": 0,
  "aggs": {
    "2": {
      "date_histogram": {
        "field": "@timestamp",
        "interval": "10m",
        "pre_zone": "-06:00",
        "pre_zone_adjust_large_interval": true,
        "min_doc_count": 1,
        "extended_bounds": {
          "min": 1451982872960,
          "max": 1452026072960
        }
      },
      "aggs": {
        "1": {
          "sum": {
            "field": "hmap_size"
          }
        }
      }
    }
  }
}'