Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"MCA Go":"1-2-3"},{"MCA Go":"2-3-4"}]
Query
db.collection.update({},[{$addFields:{MGE_ID:{$arrayElemAt:[{"$split":["$MCA Go","-"]},0]}}}],{multi:true})
Result