prepend string to entire column in mongodb

Question

I would like to prepend a string to all values of a mongo collection's column.

Something like

 db.testcoll.update({},{$set:{column1 : "prependstring"+ column1}});

Is there something like this ?

Answer 1

That can be achieved using the $concat operator in an aggregation pipeline.

db.testcoll.aggregate([{
  $project: {
    column1: {
      $concat: ['prependstring', '$column1']
    }
  }
}]);

As specified in the official MongoDB docs (here) the $concat operator only works with strings.