terms聚合时如何将没有数据的分组默认值为0返回，而不是不显示

请求

{

	"query": {

		"match_all": {}

	},

	"size": 0,

	"aggs": {

		"group": {

			"terms": {

				"field": "test",

				"size": 2

			}

		}

	}

}

返回

{

	"took": 20,

	"timed_out": false,

	"_shards": {

		"total": 1,

		"successful": 1,

		"skipped": 0,

		"failed": 0

	},

	"hits": {

		"total": {

			"value": 4,

			"relation": "eq"

		},

		"max_score": null,

		"hits": []

	},

	"aggregations": {

		"group": {

			"doc_count_error_upper_bound": 0,

			"sum_other_doc_count": 0,

			"buckets": [

				{

					"key": "abc",

					"doc_count": 4

				}

			]

		}

	}

}

{

	"took": 20,

	"timed_out": false,

	"_shards": {

		"total": 1,

		"successful": 1,

		"skipped": 0,

		"failed": 0

	},

	"hits": {

		"total": {

			"value": 4,

			"relation": "eq"

		},

		"max_score": null,

		"hits": []

	},

	"aggregations": {

		"group": {

			"doc_count_error_upper_bound": 0,

			"sum_other_doc_count": 0,

			"buckets": [

				{

					"key": "abc",

					"doc_count": 4

				},

				{

					"key": "bcd",

					"doc_count": 0

				},

				{

					"key": "cde",

					"doc_count": 0

				}

			]

		}

	}

}