如何使用mongoimport从CSV文件导入Mongodb ObjectId？

Question

I am struggling to import Mongodb's ObjectId from a CSV file using mongoimport:

I tried every combination and escape method I could think of but can't import ObjectId correctly from CSV.

First I tried importing exactly what I get exported from MongoDB to CSV. I am using MongoDB 2.2.1.

I just created two collections and referenced one document's _id in another document:

use yourdb
db.createCollection("student")
db.createCollection("class")
db.student.insert({"name":"Peter"})
db.student.find() returns { "_id" : ObjectId("5143af326d44e1ceb372121d"), "name" : "Peter" }
db.class.insert({"student_id": ObjectId("5143af326d44e1ceb372121d"),"name":"II-4"})

Then I used mongoexport command in shell:

mongoexport -h localhost:3002 -d yourdb -c classes --csv -f student_id,name > export.txt

Resulting CSV looks like this:

student_id,name
ObjectID(5143af326d44e1ceb372121d),"II-4"

Then I imported the resulting CSV using:

mongoimport -h localhost:3002 -d yourdb -c class --type csv --file export.txt --headerline

Quering class collection now returns:

db.class.find()
{ "_id" : ObjectId("5143afc66d44e1ceb372121e"), "student_id" :   ObjectId("5143af326d44e1ceb372121d"), "name" : "II-4" }
{ "_id" : ObjectId("5143b44788df173ba096550e"), "student_id" : "ObjectID(5143af326d44e1ceb372121d)", "name" : "II-4" }

As you can notice student_id field in the second document is actually a string and not MongoDB ObjectId.

I am wrong on something or Mongo can't import it's own exported CSV??

Answer 1

For anyone with this issue who's trying to insert ObjectIds from JSON - it very much IS possible with a bit of modification to the existing data.

Replace:

{ "_id" : ObjectId("5143afc66d44e1ceb372121e"),
  "student_id" : ObjectId("5143af326d44e1ceb372121d"),
  "name" : "II-4" }

With:

{ "_id" : {"$oid":"5143afc66d44e1ceb372121e"},
  "student_id" : {"$oid":"5143af326d44e1ceb372121d"},
  "name" : "II-4" }

Just use a regular expression to replace the ObjectId wrap.

Answer 2

The problem can be reproduced in MongoDB 2.4.1.

The documentation ( http://docs.mongodb.org/manual/reference/mongoimport/ ) states (emphasis by me):

Note Do not use mongoimport and mongoexport for full instance, production backups because they will not reliably capture data type information . Use mongodump and mongorestore as described in “Backup Strategies for MongoDB Systems” for this kind of functionality.

In this discussion https://groups.google.com/forum/?fromgroups=#!topic/mongodb-user/RcnumM5QyxM a similar question was answered as this:

Mongoimport with tsv or csv can only import strings and numbers , and not any of the other types specified in [1]. If you do want to import those types, and if you can produce JSON instead of TSV for your import file, that would be a good way to go; otherwise, you can write a post-processing step which converts the strings to the appropriate MongoDB types (based on some knowledge of what the type of value for a given field should be).

• Dan

[1] http://www.mongodb.org/display/DOCS/Mongo+Extended+JSON