Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"key":"!234"},]
Query
db.collection.aggregate([{"$addFields":{"newField":{$map:{input:{$range:[0,{"$strLenCP":"$key"}]},in:{"$substr":["$key","$$this",1]}}}}}])
Result