mongo copy from one collection to another (on the same db)

Question

I have got mongo db called test and in this db two collections collection1 and collection1_backup. How to replace content of col

Answer 1

simply just do this.

//drop collection1

db.collection1.drop();

//copy data from collection1_backup to collection1

db.collection1.insert(db.collection1_backup.find({},{_id:0}).toArray());