Question 117462 in Mongodb Question posted in
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Variables from values in MongoDB Arrays with variable length

This is my first question ever here so super excited to learn and apologies if the syntax is not up to mark, I will improve with time.

  1. "item" is an Array ( this doc has only one element)
  2. "adjudication" is a nested Array with a variable number of elements(same structure)
  3. I want to create keys out of "adjudication.category.coding.code" without hardcoding as the values will be different with each document but will have the same string length
  4. I tried using "$map" to apply the same logic to each array element but failed
    "item": [
      {
        "adjudication": [
          {
            "amount": {"code": "USD", "system": "4217", "value": 22.51},
            "category": {
              "coding": [
                {
                  "code": "bb.org/paid_amt",
                  "system": "bb.org/adjudication"
                }
              ]
            },
            "reason": {
              "coding": [
                {
                  "code": "C",
                  "system": "bb.org/cvrg_status"
                }
              ]
            }
          },
          {
            "amount": {"code": "USD", "system": "4217", "value": 0},
            "category": {
              "coding": [
                {
                  "code": "bb.org/discount_amt",
                  "system": "bb.org/adjudication"
                }
              ]
            }
          }
        ]
      }
    ]

Output desired

adjudication: {paid_amt: 22.51, discount_amt: 0}
Tags:

2

Answers


  1. 0

    Welcome to SO. I hope the following code will solve your exception. Sometime you may modify based on you wish.

    • $unwind to deconstruct the array
    • $map to loop / modify through the array, and $arrayElementAt to. get the first object from the array
    • $let to find the last potion by $spliting for "paid_amt" and "discount_amt". So this will be an array of object. But you need objects. So the next part I make it as k:v pair.
    • $arrayToObject to make array to object by using above k:v pair. ("k" and "v" names are must. Can’t replace by any other names)
    • $group to reconstruct the array that we did in 1st step

    Here is the code,

    db.collection.aggregate([
  { "$unwind": "$item" },
  {
    $project: {
      "item.adjudication": {
        "$map": {
          "input": "$item.adjudication",
          "in": {
            amount: "$$this.amount.value",
            code: {
              "$arrayElemAt": [ "$$this.category.coding", 0 ]
            }
          }
        }
      }
    }
  },
  {
    $project: {
      "item.adjudication": {
        "$map": {
          "input": "$item.adjudication",
          "in": {
            v: "$$this.amount",
            k: {
              "$let": {
                "vars": {
                  "code": {
                    "$split": [ "$$this.code.code", "/" ]
                  }
                },
                "in": { "$arrayElemAt": [ "$$code",  -1 ]  }
              }
            }
          }
        }
      }
    }
  },
  {
    $project: {
      "item.adjudication": {
        "$arrayToObject": "$item.adjudication"
      }
    }
  },
  {
    "$group": {
      "_id": "$_id",
      "item": {  "$push": "$item" }
    }
  }
])

    Working Mongo playground

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  2. 0

    try this playground

    db.collection1.aggregate(
[{
    $unwind: {
        path: '$item'
    }
}, {
    $unwind: {
        path: '$item.adjudication'
    }
}, {
    $unwind: {
        path: '$item.adjudication.category'
    }
}, {
    $unwind: {
        path: '$item.adjudication.category.coding'
    }
}, {
    $group: {
        _id: null,
        data: {
            $push: {
                k: '$item.adjudication.category.coding.code',
                v: '$item.adjudication.amount.value'
            }
        }
    }
}, {
    $project: {
        _id:0,
        adjudication: {$arrayToObject: '$data'}
    }
}]
)
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