mongo copy from one collection to another (on the same db)

Question

I have got mongo db called test and in this db two collections collection1 and collection1_backup. How to replace content of col

Answer 1

simply just do this.

//drop collection1

db.collection1.drop();

//copy data from collection1_backup to collection1

db.collection1.insert(db.collection1_backup.find({},{_id:0}).toArray());

Answer 2

Using Java Driver

Try below one:

public void copyTo(String db,String sourceCollection,String destinationCollection,int limit) throws        
UnknownHostException {

    MongoClient mongo = new MongoClient("localhost", 27017);
    DB database = mongo.getDB(db);
    DBCollection collection = database.getCollection(sourceCollection);
    DBCursor dbCursor = collection.find().limit(limit);
    List<DBObject> list =  dbCursor.toArray();
    DBCollection destination =  database.getCollection(destinationCollection);
    destination.insert(list, WriteConcern.NORMAL); //WRITE CONCERN is based on your requirment.

}

Answer 3

You can use a simple command to Backup MongoDB Collection. It will work only on MongoDB 4.0 or earlier versions.

db.sourceCollectionName.copyTo('targetCollectionName')

Your targetCollectionName must be in Single(') or Double(") Quote

Note:

The db.collection.copyTo() method uses the eval command internally. As a result, the db.collection.copyTo() operation takes a global lock that blocks all other read and write operations until the db.collection.copyTo() completes.

Answer 4

also usefull: to export collection to json file

mongoexport --collection collection1_backup --out collection1.json

to import collection from json file

mongoimport --db test --collection collection1 --file collection1.json

to import single collection from backup/dump file one need to convert *.bson file to *.json by using

bsondump collection1_backup.bson > collection1_backup.json

Answer 5

This can be done using simple command:

db.collection1_backup.aggregate([ { $match: {} }, { $out: "collection1" } ])

This command will remove all the documents of collection1 and then make a clone of collection1_backup in collection1.

Generic Command would be

db.<SOURCE_COLLECTION>.aggregate([ { $match: {} }, { $out: "<TARGET_COLLECTION>" } ])

If TARGET_COLLECTION does not exist, the above command will create it.

Answer 6

The best way to have done this (considering the name of the collection ends with _backup) is possibly to have used mongorestore: http://docs.mongodb.org/manual/reference/mongorestore/

However in this case it depends. If the collection is unsharded you can use renameCollection ( http://docs.mongodb.org/manual/reference/command/renameCollection/ ) or you can use a more manual method of (in JavaScript code):

db.collection1.drop(); // Drop entire other collection
db.collection1_backup.find().forEach(function(doc){
   db.collection1.insert(doc); // start to replace
});

Those are the most common methods of doing this.