In mongo console I can clone a collection really fast by using the aggregate method, like this:

db.sourcecollection.aggregate([\{$out: "targetcollection"}])

Unfortunately, $out is not implemented in ruby driver.

The only current way to clone a collection in ruby is by going through the documents. There should be the possibility to run the aggregation with '$out' in the pipeline. There is huge difference in terms of efficiency, especially when dealing with large collections.

Thanks for reading this, i hope to be hearing from you soon.