erpGoodsId、batchNum 和 wmsProductCode 三个字段分组后，怎么获取所有分组的总数

在 Elasticsearch 的聚合语句中，可以使用 `cardinality` 聚合来计算某个字段的去重值个数，从而得到分组的总数。具体的做法是，在 `composite` 聚合的外层，再套一层 `cardinality` 聚合，如下所示：

{
  "query": {
    "bool": {
      "should": [
        {
          "match": {
            "erpSupplierFlowId": "1001E111230001IPJP6W"
          }
        },
        {
          "match": {
            "erpSupplierFlowId": "1001A110000001CBWJ0I"
          }
        },
        {
          "match": {
            "erpSupplierFlowId": "1001A110000001IPM06S"
          }
        },
        {
          "match": {
            "companyCode": "10101"
          }
        }
      ]
    }
  },
  "size": 0,
  "track_total_hits": false,
  "aggs": {
    "my_buckets": {
      "composite": {
        "size": 1000,
        "sources": [
          {
            "erpGoodsId": {
              "terms": {
                "field": "erpGoodsId",
                "order": "asc"
              }
            }
          },
          {
            "batchNum": {
              "terms": {
                "field": "batchNum",
                "order": "asc"
              }
            }
          },
          {
            "wmsProductCode": {
              "terms": {
                "field": "wmsProductCode",
                "missing": "null",
                "order": "asc"
              }
            }
          }
        ]
      },
      "aggs": {
        "filter_empty_dest": {
          "bucket_selector": {
            "buckets_path": {
              "count": "_count"
            },
            "script": "params.count != null"
          }
        }
      }
    },
    "total_groups": {
      "cardinality": {
        "fields": [
          "erpGoodsId",
          "batchNum",
          "wmsProductCode"
        ]
      }
    }
  }
}

在聚合结果中，`total_groups` 聚合的 `value` 字段即为分组的总数。