MongoDB: forEach vs fetch + each

Question

When I want to iterate over some set of documents stored in MongoDB from my Meteor application, I can use

db.collection.find( ... ).forEach( function f( doc ){ ... })

or

var docs = db.collection.find( ... ).fetch();
_.each( docs, function f( doc ){ ... }); // using underscore.js

Which method is preferable in terms of performance? What are the pros and cons for both options?

Answer 1

Both operators do basically the same thing at the core API level, which gets the cursor and converts the results. However, there is one “main” performance difference:

• .forEach() will broadcast the results of the cursor "one at a time" and process the iterator function it performs.

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