My collection

[
  {
    "_id": "value",
    "data": [
      {
        "d": "2022-05-16",
        "v": 10.06
      },
      {
        "d": "2022-05-18",
        "v": 9.11
      },
      {
        "d": "2022-05-20",
        "v": 7.06
      }
    ],
    "name": "Vegeta"
  }
]

Now I want to make a query say

{name : "something" , "data.d" : "2022-05-18"} --> this filter returns v = 9.11
{name : "something" , "data.d" : "2022-05-17"} --> this filter also should return v = 10.06
{name : "something" , "data.d" : "2022-05-19"} --> this filter also should return v = 9.11

Basically I want to the return the result from data which matches the given date if not present then return the previous date data.

I have tried using elemmatch. Unwind works for me but need to increase the performance of the query.If possible can we do in the mongo shell itself.

CodePudding user response：

db.collection.aggregate([
  {
    $match: {
      "name": "Vegeta"  //input
      
    }
  },
  {
    "$project": {
      "_id": 1,
      "name": 1,
      "data": {  //filter the array elements
        "$filter": {
          "input": "$data",
          "as": "data",
          "cond": {
            "$lte": [
              "$$data.d",
              "2022-05-20"  //input
              
            ]
          }
        }
      }
    }
  },
  {
    $project: {
      "_id": 1,
      "name": 1,
      "data": {  //sort the remaining array elements
        $sortArray: {
          input: "$data",
          sortBy: {
            "d": -1
          }
        }
      }
    }
  },
  {
    $project: {
      "_id": 1,
      "name": 1,
      "data": {  //pick one
        "$arrayElemAt": [
          "$data",
          0
        ]
      }
    }
  }
])

Mongo Playground