Facing issue with Mongoexport json file "_id" column - json

Question

I am exporting mongo collection to json format and then loading that data to bigquery table using bq load command.
mongoexport --uri mongo_uri --collection coll_1 --type json --fields id,createdAt,updatedAt --out data1.csv
The json row looks like below:
{"_id":{"$oid":"6234234345345234234sdfsf"},"id":1,"createdAt":"2021-05-11 04:15:15","updatedAt":null}
but when i run bq load command in bigquery it gives below error:
Invalid field name "$oid". Fields must contain only letters, numbers, and underscores, start with a letter or underscore, and be at most 300 characters long.
I think if mongoexport json contains {"_id": ObjectId(6234234345345234234sdfsf)} , my issue will be solved.
Is there any way to export json like this?
Or any other way to achive this?
Note: i can't use csv format because mongo documents contain commas.

Answer 1

By default, _id holds an ObjectId value, so it's better to store data in {"_id": ObjectId(6234234345345234234sdfsf)} format instead of storing it in "_id":{"$oid":"6234234345345234234sdfsf"}.
As you mentioned if json contains {"_id": ObjectId(6234234345345234234sdfsf)} your problem will be solved.

Answer 2

Replace $oid with oid. I'm using Python, so the code below worked:
with fileinput.FileInput("mongoexport_json.txt", inplace=True, encoding="utf8") as file:
for line in file:
print(line.replace('"$oid":', '"oid":'), end='')