Question

In my upsert request, I’d like to both:

• update the object in place if it’s there, aka

  db.somecollection.update({x: 1}, {$inc: {x: 1}});
  

• provide a new object if it’s not there, aka

  db.somecollection.update({x: 1}, {whole: 0, new: 'yata', object: 42});
  

Is there a way to do that ?

The problem is that upsert seems to work only if you already provide an object in the first place, not a modifier.

edit: I’ll be more specific.

I want to update objects of the form

{_id: 12, a: 123, b: 234, c: 345}

my update is just an increment of 1 on one of a, b or c. If the object is not in the base then I’d like to create an object of the form

{_id: 13, a: 1, b: 0, c: 0}

if a was the field I was trying to increment.

Now, if I read the manual correctly, I can write

db.somecollection.update({_id: 12}, {$inc: {a: 1}}, true);

which will work fine to update my a field but which will not create the fields b and c if the object doesn’t exist.

Answer 1

Upserts can work with modifiers; the modifier gets applied to the selector/criteria object when a new document needs to be created. See here. But you do need to set the upsert parameter to true in your update call:

db.somecollection.update({x: 1}, {$inc: {x: 1}}, true);

UPDATE

To get the behavior you’re looking for:

db.somecollection.update({_id: 12}, {$inc: {a: 1, b: 0, c: 0}}, true);