MongoDB Split document field into two fields - json

Question

I have a MongoDB document with over 2.8m documents of common passwords (hashed in SHA1) and their popularity.
Currently I've imported the documents with the following schema
{"_id":"5ded1a559015155eb8295f48","password":"20EABE5D64B0E216796E834F52D61FD0B70332FC:2512537"}
Although I'd like to split this so I can have the popularity value and it would look something like this
{"_id":"5ded1a559015155eb8295f48","password":"20EABE5D64B0E216796E834F52D61FD0B70332FC","popularity":2512537}
Question is im unsure how I can split the password into two password, popularity using : to split the string

Answer 1

You can use Aggregation Framework to split current password into two fields. You need to start with $indexOfBytes to get the position of : and then you need $substr to create new fields based on evaluated position.
db.collection.aggregate([
{
$addFields: {
colonPos: { $indexOfBytes: ["$password",":"] }
}
},
{
$addFields: {
password: { $substr: [ "$password", 0, "$colonPos" ] },
popularity: { $substr: [ "$password", "$colonPos", { $strLenBytes: "$password" } ] }
}
},
{
$project: {
colonPos: 0
}
}
])
Mongo Playground
As a last step you can use $out which takes all your aggregation results and writes them into new or existing collection.
EDIT: Alternative approach using $split (thank to #matthPen):
db.collection.aggregate([
{
$addFields: {
password: { $arrayElemAt: [ { "$split": [ "$password", ":"] }, 0 ] },
popularity: { $arrayElemAt: [ { "$split": [ "$password", ":"] }, 1 ] }
}
}
])
Mongo Playground