在 MongoDB 中使用 $function new 运算符进行 updateMany 失败

Question

I have an array tree and I want to update that array in my collection with this syntax

db.documents.updateMany(
  {
    companyId: ObjectId("5f29074048538b6403bc71ab",
    tree: {
      $in: [ObjectId("5f539bf696fa1748fa417b07")],
    },
  },
  [{
    $set: {
      tree: {
        $function: {
          body:
            "function(t) { t.push(ObjectId('5f5494a1d708bda4988d75d4')); return t.filter(v => [ObjectId('5f539bf696fa1748fa417b07')].includes(v))}}",
          args: ["$tree"],
          lang: "js",
        },
      },
    },
  }]
);

why I write body function with string? because in Golang I can't use code for bson, so I must use function string, the syntax above is I run on command line mongo cli to try there first then implement to my Go app

the error I got is

Unrecognized expression '$function'

anyone has same problem ? or I did wrong to use $function operator ??

Answer 1

I had this problem too. In my scenario, the problem was the version of MongoDB instance. Check the documentations of $function https://docs.mongodb.com/manual/reference/operator/aggregation/function/ , it says the functions was introduced in version 4.4 If you any doubts about the version you're running just execute "db.version()". Mine was 4.2.17

I hope it can help