- I want to copy full collection (e.g. name ‘home’).
- Then do some changes in the ‘home’ collection or remove doc inside it (not a collection).
- And then replace changed ‘home’ collection to its default state from item 1.
I do next:
db = client["database"] home = db['home'].find() # get collection. db['home'].remove({}) # remove doc from home for i in home: self.db['home'].insert(i)
But the collection is empty.
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Answer
The problem with your code example is that find()
returns a database cursor to the collection, not all documents in the collection. So when you remove
all documents from the home
collection, the cursor will also point to an empty collection.
In order to copy a collection to another collection in the same server, you can utilise MongoDB Aggregation operator $match and $out
pipeline = [ {"$match": {}}, {"$out": "destination_collection"}, ] db.source_collection.aggregate(pipeline)
Using your example code, now you can do
source = db["source_collection"] destination = db["destination_collection"] # Remove all documents, or make modifications. source.remove({}) # Restore documents from the source collection. for doc in destination: source.insert(doc) # or instead you can just use the same aggregation method above but reverse the collection name.
Note : db.collection.copyTo() has been deprecated since MongoDB v3.0.
If you would like to copy to another MongoDB server, you can utilise db.cloneCollection(). In PyMongo it would be a command such below:
db.command("cloneCollection", **{'collection': "databaseName.source_collection", 'from': "another_host:another_port"})
Depending on your overall goal, you may find MongoDB BackUp methods useful.