ElasticSearch script查询报错A document doesn‘t have a value for a field! Use doc[＜field＞].size()==0

ES版本7.6.0
想筛选某两个字段之和大于10的文档，需要用到脚本，简化的请求如下

{
  "query":
  {
    "bool":
    {
      "must":
      [
        {
          "script":
          {
            "script": "doc['field'].value >= 1"
          }
        }
      ]
    }
  }
}

报非法状态异常，其实报错提示大概也讲清楚了，“A document doesn’t have a value for a field!”（有一个文档的字段没有值），不过总觉得指示清楚哪个文档哪个字段不是更友好么；并且也给出了解决方案：用doc[].size()==0检查文档是否缺失字段

{
  "error" : {
    "root_cause" : [
      {
        "type" : "script_exception",
        "reason" : "runtime error",
        "script_stack" : [
          "org.elasticsearch.index.fielddata.ScriptDocValues$Longs.get(ScriptDocValues.java:121)",
          "org.elasticsearch.index.fielddata.ScriptDocValues$Longs.getValue(ScriptDocValues.java:115)",
          "doc[\"field\"].value >= 1",
          "                  ^---- HERE"
        ],
        "script" : "doc[\"field\"].value >= 1",
        "lang" : "painless"
      }
    ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [
      {
        "shard" : 0,
        "index" : "...",
        "node" : "...",
        "reason" : {
          "type" : "script_exception",
          "reason" : "runtime error",
          "script_stack" : [
            "org.elasticsearch.index.fielddata.ScriptDocValues$Longs.get(ScriptDocValues.java:121)",
            "org.elasticsearch.index.fielddata.ScriptDocValues$Longs.getValue(ScriptDocValues.java:115)",
            "doc[\"field\"].value >= 1",
            "                  ^---- HERE"
          ],
          "script" : "doc[\"field\"].value >= 1",
          "lang" : "painless",
          "caused_by" : {
            "type" : "illegal_state_exception",
            "reason" : "A document doesn't have a value for a field! Use doc[].size()==0 to check if a document is missing a field!"
          }
        }
      }
    ]
  },
  "status" : 400
}

ES7.0更新中也提到了

Accessing missing document values will throw an error
doc['field'].value will throw an exception if the document is missing a value for the field field.

To check if a document is missing a value, you can use doc['field'].size() == 0.

解决方法：加入空检查

{
  "query":
  {
    "bool":
    {
      "must":
      [
        {
          "script":
          {
            "script":
            {
              "source": "doc[\"field\"].size() != 0 && doc[\"field\"].value > 1"
            }
          }
        }
      ]
    }
  }
}