Mongodb Question posted in
The official documentation can be found here.

How to convert a positive integer to binary inside mongoDB aggregation

I was looking for a way to convert a positive integer into a binary array inside a mongoDB aggregation pipeline.

There is $bit operation which can’t be used inside an aggregation pipeline.

This question is regarding mongoDB version 6.0 and older

Input example data:

[
  {_id: 1, integerInput: 13},
  {_id: 2, integerInput: 3 },
  {_id: 3, integerInput: 1 },
  {_id: 4, integerInput: 17},
  {_id: 5, integerInput: 10}
]

Requested output:

[
  {_id: 1, integerInput: 13, binary: [1, 1, 0, 1]},
  {_id: 2, integerInput: 3 , binary: [1, 1]},
  {_id: 3, integerInput: 1 , binary: [1]},
  {_id: 4, integerInput: 17, binary: [1, 0, 0, 0, 1]},
  {_id: 5, integerInput: 10, binary: [1, 0, 1, 0]}
]
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    One option is to do the calculation using $map with $range and $log operations:

    db.collection.aggregate([
  {$set: {
      binary: {$reverseArray: {
          $map: {
            input: {$concatArrays: [
                [0],
                {$range: [1, {$ceil: {$log: ["$integerInput", 2]}}]}
            ]},
            in: {$mod: [
                {$floor: {$divide: [
                      "$integerInput",
                      {$pow: [2, "$$this"]}
                ]}},
                2
            ]}
          }
      }}
  }}
])

    See How it works on the mongoDB playground


  2. 0

    Binary functions in Aggregation Framework are very limited. Performance wise this one should be better:

    db.collection.aggregate([
   {
      $set: {
         binary: {
            $function: {
               body: function (val) {
                  return val.toString(2).split('').map(x => parseInt(x));
               },
               args: ["$integerInput"],
               lang: "js"
            }
         }
      }
   }
])
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search