var all_size = 0;
var collectionNames = db.getCollectionNames(), stats = [];
collectionNames.forEach(function (n) {
var cursor = db[n].find({
_id: {
$gt: ObjectId("619124700000000000000000"),
$lt: ObjectId("619275f00000000000000000"),
},
});
var size = 0;
cursor.forEach(function (doc) {
size += Object.bsonsize(doc);
});
all_size += size;
});
print(all_size);