es5.5版本,执行下面单个的date_histogram或者scripted_metric都是没问题的,但是嵌套起来就报错

{

    "aggs": {

        "kpi": {

            "date_histogram": {

                "field": "time",

                "interval": "1h"

            },

            "aggs": {

                "kpi": {

                    "scripted_metric": {

                        "init_script": "params._agg['subtract'] = []",

                        "map_script": "params._agg.subtract.add([doc.a.value + doc.b.value,doc.c.value + doc.d.value])",

                        "combine_script": "double total1=0;double total2=0;  for (i in params._agg.subtract) { total1 += i[0]; total2 += i[1] } return [total1, total2]",

                        "reduce_script": "double total1=0; double total2=0; for (item in params._aggs) { total1 += item[0]; total2 += item[1]} return total1 / total2"

                    }

                }

            }

        }

    }

}

{

  "error": {

    "root_cause": [],

    "type": "search_phase_execution_exception",

    "reason": "",

    "phase": "fetch",

    "grouped": true,

    "failed_shards": [],

    "caused_by": {

      "type": "script_exception",

      "reason": "runtime error",

      "script_stack": [

        "total1 += item[0]; ",

        "^---- HERE"

      ],

      "script": "double total1=0; double total2=0; for (item in params._aggs) { total1 += item[0]; total2 += item[1]} return total1 / total2",

      "lang": "painless",

      "caused_by": {

        "type": "null_pointer_exception",

        "reason": null

      }

    }

  },

  "status": 503

}