MongoDB Search by property name for any Document with that property

Question

How do I do a search in MongoDB that searches for any documents with a given property?

What I want to do is find all the documents that have the property regardless of it's value and I don't seem to be able to do this. I've tried the following

db.collection.find({"property", null}); //Finds things that don't have that property
db.collection.find({"proprety", {}}); //Doesn't find anything unless something has the empty object as the value

Is there actually a syntax for this or would I need to do a mapreduce operation?

Answer 1

Here's the sample answer using $exists:

db.collection.find( { property : { $exists: true } } );

Answer 2

Just invert the query and search for documents where the property is not null ($ne not equals)

db.collection.find( { property : { $ne : null } } );