Mongo: Move json string to a part of the document - json

Question

I have a mongo collection where documents have aprox the following structure:
item{
data{"emailBody":
"{\"uniqueKey\":\" this is a stringified json\"}"
}
}
What I want to do is to use 'uniqueKey' as an indexed field, to make an "inner join" equivalant with items in a different collection.
I was thinking about running a loop on all the documents -> parsing the json -> Saving them as new property called "parsedEmailBody".
Is there a better way to handle stringified json in mongo?

Answer 1

The only way is to loop through the collection, parse the field to JSON and update the document in the loop:
db.collection.find({ "item.data.emailBody": { "$type": 2 } })
.snapshot().forEach(function(doc){
parsedEmailBody = JSON.parse(doc.item.data.emailBody);
printjson(parsedEmailBody);
db.collection.updateOne(
{ "_id": doc._id },
{ "$set": { "item.data.parsedEmailBody": parsedEmailBody } }
);
});
For large collections, leverage the updates using the Bulk API:
var cursor = db.collection.find({ "item.data.emailBody": { "$type": 2 } }).snapshot(),
ops = [];
cursor.forEach(function(doc){
var parsedEmailBody = JSON.parse(doc.item.data.emailBody);
ops.push({
"updateOne": {
"filter": { "_id": doc._id },
"update": { "$set": { "item.data.parsedEmailBody": parsedEmailBody } }
}
});
if (ops.length === 500) {
db.collection.bulkWrite(ops);
ops = [];
}
});
if (ops.length > 0) { db.collection.bulkWrite(ops); }