Unrecognized expression Error in Aggregation Projection Query

Question

Invalid $project :: caused by :: Unrecognized expression '$$varientPricePoint.ppId'

{
  "pricepoint": {
    "$filter": {
      "input": "$OriginalPricePoints",
      "as": "varientPricePoint",
      "cond": {
        "$$varientPricePoint.ppId": {
          "$in": ["PP100"]
        }
      }
    }
  },
  "_id": 0
}

Answer 1

You can't use the variable as the root object key, instead you need wrap with $in operator as below:

{
  "pricepoint": {
    "$filter": {
      "input": "$OriginalPricePoints",
      "as": "varientPricePoint",
      "cond": {
        $in: [
          "$$varientPricePoint.ppId",
          ["PP100"]
        ]
      }
    }
  }
}