MongoDB Array Filters

Question

I am trying to update an nested array using Array filters, for hands on first i am trying with basic array filter update query, i copied pasted the update query from the mongodb tutorial, But i am getting error like: Error:"No array filter found for identifier 'elem' in path 'grades.$[elem].mean' "and i am using 'db version v4.0.2' and 'MongoDB shell version v4.0.2

Here is my collection Details,

              {
              "_id" : 1,
              "grades" : [ 
              {
              "grade" : 80,
              "mean" : 75,
              "std" : 6
              }, 
              {
              "grade" : 85,
              "mean" : 90,
              "std" : 4
              }, 
              {
              "grade" : 85,
              "mean" : 85,
              "std" : 6
              }
              ]
              }
             //End of First Record
              {
              "_id" : 2,
              "grades" : [ 
               {
              "grade" : 90,
              "mean" : 75,
              "std" : 6
              }, 
              {
             "grade" : 87,
             "mean" : 90,
             "std" : 3
             }, 
             {
            "grade" : 85,
            "mean" : 85,
            "std" : 4
            }     
            ]
            }
            //End of Second record 

update Query:

          db.getCollection('students2').update(

         {   },
         { $set: { "grades.$[elem].mean" : 100 } },
         {
          multi: true,
          arrayFilters: [ { "elem.grade": { $gte: 85 } } ]
          }
          )

Throw's the Error: No array filter found for identifier 'elem' in path 'grades.$[elem].mean'

Answer 1

Read the comments of this StackOverflow issue:

arrayFilters not working

It doesn't work in "older shells". I'm using the Robo 3T client and running into the same issue. The shell is apparently removing the arrayFilters object.