查詢返回指定的elasticsearch文檔字段

可以通過指定elasticsearch中文檔的字段，來指定返回文檔中的字段：

通過_source字段來指定需要返回的字段。

舉例：根據關係單號，查詢es，只需要返回salesType，policyNo，policyRelationNo,policyStatus

{
  "_source": [
    "salesType",
    "policyNo",
    "policyRelationNo",
    "policyStatus"
  ],
  "query": {
    "bool": {
      "must": [
        {
          "term": {
            "policyRelationNo": "KR01435021"
          }
        }
      ],
      "should": [],
      "must_not": []
    }
  },
  "from": 0,
  "size": 10
}

效果如下：

{
	"_shards": {
		"total": 5,
		"successful": 5,
		"failed": 0
	},
	"hits": {
		"total": 19,
		"max_score": 11.391884,
		"hits": [
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407038",
				"_score": 11.391884,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120319",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407056",
				"_score": 10.877399,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120328",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407052",
				"_score": 10.877399,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120326",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407062",
				"_score": 10.877399,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120331",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407064",
				"_score": 10.877399,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120332",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407054",
				"_score": 10.871439,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120327",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407050",
				"_score": 10.871439,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120325",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407068",
				"_score": 10.871439,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120334",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407042",
				"_score": 10.871439,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120321",
					"policyStatus": 11
				}
			},
			{
				"_index": "search4policy-msad-dev3_20200520000000",
				"_type": "policy-msad-dev3",
				"_id": "4407046",
				"_score": 10.713255,
				"_source": {
					"salesType": "100070600000",
					"policyRelationNo": "KR01435021",
					"policyNo": "B609120323",
					"policyStatus": 11
				}
			}
		]
	},
	"took": 29,
	"timed_out": false
}

優點：按需所取，可以提供elasticsearch的響應(類似你sql查詢，查全表字段的耗時和查你所需的字段的耗時一個道理)