Mongodb _id Value and Indexes Are Lost During Mongorestore

Question

Steps I used:

1. mongodump
2. copy dump folder to another computer (for each collection I get .bson and metadata files)
3. mongorestore myDumpFolder

I noticed the indexes are lost and _id has new values after mongorestore.

Can anyone share their restore experiences that restored both indexes and mongodb_id?

Answer 1

Can anyone share their restore experiences that restored both indexes and mongodb_id?

As per MongoDB documentation here By default, mongorestore looks for a database backup in the dump/ directory.

New in version 3.6:

All MongoDB collections have UUIDs by default. When MongoDB restores collections, the restored collections retain their original UUIDs. When restoring a collection where no UUID was present, MongoDB generates a UUID for the restored collection.

UUID() has the following syntax:

UUID(<string>)

Parameter   Type    Description
hex        string   
                    Optional. Specify a 36 character string to convert to a UUID BSON object. If not provided, MongoDB generates a random UUID in RFC 4122 v4 format.

Changed in version 3.6: In earlier versions of the mongo shell, UUID required a hexadecimal string argument. See the 3.4 manual.

It's returns A BSON UUID object.

I noticed the indexes are lost and _id has new values after mongorestore.

@Will, As JJussi has already said that mongorestore should recreate all indexes what mongodump has recorded.

For Example

I have mongodump in my C:\data\dump folder. Which contains the database folder 100YWeatherSmall,citibike,city,ships,video with their (.bson & .json) file. These database I had already restored in MongoDB 3.6.

Here again i am going to mongorestore to these databases dump file in MongoDB 3.6.

As you can see that mention all databases has already in MongoDB.

Note: Here I have highlighted the some database name due to security reason.

Here I am going to mongorestore through the below command.

C:\Program Files\MongoDB\Server\3.6\bin>mongorestore --verbose C:\data\dump

Note: Run mongorestore from the system command line, not the mongo shell.

video.movies database dump restore report status

- E11000 duplicate key error collection: video.movies index: _id_ dup key: { : ObjectId('58c59c6b99d4ee0af9e0eef0') }
  - E11000 duplicate key error collection: video.movies index: _id_ dup key: { : ObjectId('58c59c6b99d4ee0af9e0eef1') }
  - E11000 duplicate key error collection: video.movies index: _id_ dup key: { : ObjectId('58c59c6b99d4ee0af9e0eef2') }
  - E11000 duplicate key error collection: video.movies index: _id_ dup key: { : ObjectId('58c59c6b99d4ee0af9e0eef3') }
  - E11000 duplicate key error collection: video.movies index: _id_ dup key: { : ObjectId('58c59c6b99d4ee0af9e0eef4') }

100YWeatherSmall.data database dump restore report status

- E11000 duplicate key error collection: 100YWeatherSmall.data index: _id_ dup key: { : ObjectId('5553a98ee4b02cf7150e1cc8') }
  - E11000 duplicate key error collection: 100YWeatherSmall.data index: _id_ dup key: { : ObjectId('5553a98ee4b02cf7150e1cca') }
  - E11000 duplicate key error collection: 100YWeatherSmall.data index: _id_ dup key: { : ObjectId('5553a98ee4b02cf7150e1ccc') }
  - E11000 duplicate key error collection: 100YWeatherSmall.data index: _id_ dup key: { : ObjectId('5553a98ee4b02cf7150e1ccd') }
  - E11000 duplicate key error collection: 100YWeatherSmall.data index: _id_ dup key: { : ObjectId('5553a98ee4b02cf7150e1cd0') }

citibike.trips database dump restore report status

 - E11000 duplicate key error collection: citibike.trips index: _id_ dup key: { : ObjectId('572bb8232b288919b68b258e') }
  - E11000 duplicate key error collection: citibike.trips index: _id_ dup key: { : ObjectId('572bb8232b288919b68b25ad') }
  - E11000 duplicate key error collection: citibike.trips index: _id_ dup key: { : ObjectId('572bb8232b288919b68b2608') }
  - E11000 duplicate key error collection: citibike.trips index: _id_ dup key: { : ObjectId('572bb8232b288919b68b26c5') }
  - E11000 duplicate key error collection: citibike.trips index: _id_ dup key: { : ObjectId('572bb8232b288919b68b26da') }

Here you can noticed that all during mongorestore it's showing index: _id_ dup key: because that index: id is already exist in that database & collection .

That means whatever mongodump has created the index:id & ObjectId that is same index:id & ObjectId is same mongorestore in MongoDB.

Here the below mention reports is the citibike.trips mongorestore complete mongodump restore reports.

2018-05-30T10:56:31.962+0300    [########################]  citibike.trips  835MB/835MB  (100.0%)
2018-05-30T10:56:31.962+0300    restoring indexes for collection citibike.trips from metadata
2018-05-30T10:56:32.106+0300    finished restoring citibike.trips (1990273 documents)
2018-05-30T10:56:32.126+0300    done

For example here I have only mention the citibite.trips restore complete reports. The message is showing restoring indexes for collection citibike.trips from metadata.

So, as per above conclusion we can say that mongorestore, store the same index:_id_ & ObjectId, which mongodump has created.

For your further ref here , here and here