How do I write a jolt transform spec to iterate through a loop?-CodePudding

I have the following

Input JSON :

{
  "a": [
    [
      "a1"
    ],
    [
      "a2"
    ]
  ],
  "b": [
    [
      "b1",
      "b2"
    ],
    [
      "b3",
      "b4"
    ]
  ]
}

I want to use jolt transform to output it like this:

Output JSON:

[
  {
    "a": "a1",
    "b": "b1"
  },
  {
    "a": "a1",
    "b": "b2"
  },
  {
    "a": "a2",
    "b": "b3"
  },
  {
    "a": "a2",
    "b": "b4"
  }
]

I use combination of shift and cardinality but can't seem to get it to iterate through correctly:

[
  {
    "operation": "shift",
    "spec": {
      "*": "&"
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "[&].&1"
      }
    }
  },
  {
    "operation": "cardinality",
    "spec": {
      "*": {
        "*": "ONE"
      }
    }
  }
]

What do I need to change to that jolt transform spec to get it to work?

CodePudding user response：

You can walk by the indexes of the array "b" while picking values from the array "a" as well such as

[
  {
    // partition by indexes of array "a"&"b" while strolling through the array "b"
    "operation": "shift",
    "spec": {
      "b": {
        "*": {
          "@(2,a)": {
            "*": "&.&1.a"
          },
          "*": "&1.&.&2"
        }
      }
    }
  },
  {
    // get rid of object labels
    "operation": "shift",
    "spec": {
      "*": {
        "*": ""
      }
    }
  },
  {
    // get rid of square brackets wrapping up the values of the attributes "a"
    "operation": "cardinality",
    "spec": {
      "*": {
        "a": "ONE"
      }
    }
  },
  {
    // order the attributes by the key names
    "operation": "sort"
  }
]

the demo on the site