利用DTL对Sesam中的深层实体结构进行平坦化

Question

Sesam文档展示了一种扁平列表的方法，但是如何才能使更深层次的结构变得像这样呢？文档指定它不能递归地扁平。

"logdata": {
  "metrics": {
    "entities": {
      "entities_per_second": "~f463.18217846895715"
    }
  }
}

Answer 1

您可以使用进行递归平坦，请参见下面的示例：

{
  "_id": "recursive-flattening",
  "type": "pipe",
  "source": {
    "type": "embedded",
    "entities": [{
      "_id": "foo",
      "value": {
        "logdata": {
          "metrics": {
            "entities": {
              "entities_per_second": "~f463.18217846895715"
            }
          }
        }
      }
    }]
  },
  "transform": {
    "type": "dtl",
    "rules": {
      "default": [
        ["copy", "*"],
        ["add", "flattened",
          ["apply", "flatten-dict", "_S.value"]
        ]
      ],
      "do-flatten": [
        ["if",
          ["is-dict", "_S.value"],
          ["merge",
            ["apply", "do-flatten",
              ["key-values",
                ["map-dict",
                  ["concat", "_S.key", "_", "_."], "_.", "_S.value"]
              ]
            ]
          ],
          ["add", "_S.key", "_S.value"]
        ]
      ],
      "flatten-dict": [
        ["merge",
          ["apply", "do-flatten",
            ["key-values", "_S."]
          ]
        ]
      ]
    }
  }
}

这将产生以下结果：

{
  "flattened": {
    "logdata_metrics_entities_entities_per_second": "~f463.18217846895715"
  },
  "value": {
    "logdata": {
      "metrics": {
        "entities": {
          "entities_per_second": "~f463.18217846895715"
        }
      }
    }
  }
}