How to update inner most nested key in mongoDB-CodePudding

I have a documents as follows:

Document 1:

{ 
    "ARCM Sum" : {
        "MCA Go" : "60", 
        "Assess" : "5030", 
        "ActivitID" : "467144" 
        "Activity Checks" : [
            {
                "Frequency within Activity Description matches Activity Frequency" : "Exception", 
                "Activity Description contains > 20 word" : "Pass"
            }
        ]
       
        "Week" : "04-05-2021", 
        "Load Datetime" : "07-14-2021"
    }
}

Document 2:

{ 
    "ARCM Sum" : {
        "MCA Go" : "60", 
        "Assess" : "5030", 
        "ActivitID" : "467144" 
        "Activity Checks" : [
            {
                "Frequency within Activity Description matches Activity Frequency" : "Exception", 
                "Activity Description contains > 20 words" : "Pass"
            }
        ]
       
        "Week" : "04-05-2021", 
        "Load Datetime" : "07-14-2021"
    }
}

I need to update document from "word" to "words" in "Activity Description contains > 20 word" , so

for example in Document 1 there is "Activity Description contains > 20 word" need to update to "Activity Description contains > 20 words"

Document 2 will be ignored as it already has words in "Activity Description contains > 20 words"

CodePudding user response：

Usually you would use $rename but because it is a field in an array you can't do it directly. Here you could use an update with an aggregation pipeline, that $maps the relevant documents:

This is available since MongoDB 4.2 Update with aggregation pipeline

db.test.update(
  { "ARCM Sum.Activity Checks.Activity Description contains > 20 word": {"$exists": true} },
  [{
    "$set": {
      "ARCM Sum.Activity Checks": {
        "$map": {
          "input": "$ARCM Sum.Activity Checks",
          "in": {
            "Frequency within Activity Description matches Activity Frequency": "$$this.Frequency within Activity Description matches Activity Frequency",
            "Activity Description contains > 20 words": "$$this.Activity Description contains > 20 word"
          }
        }
      }
    }
  }],
  { multi: true }
)