MongoDb: Difference between $push/$addtoset

Question

I read the documentation in the MongoDb and I used a simple proves and I only look that: Push is sorting the array but addtoSet isn\'t it.

For me visual

Answer 1

$push: Inserts the value to an array in the resulting document. eg;

db.mycol.aggregate([{$group : {_id : "$by_user", url : {$push: "$url"}}}])

$addToSet: Inserts the value to an array in the resulting document but does not create duplicates. eg;

db.mycol.aggregate([{$group : {_id : "$by_user", url : {$addToSet : "$url"}}}])