Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{_id:1},{_id:2,version:"123"},{_id:3,version:"456"},{_id:4,version:789}]
Query
db.collection.update({version:{$type:"string"}},[{$set:{version:{$toLong:"$version"}}}],{multi:true})
Result