The drop_index() library function in PyMongo is used to drop the index from a collection in the database, as the name suggests. In this article, we are going to discuss how to remove an index from a collection using our python application with PyMongo.
Syntax:
drop_index(index_or_name, session=None, **kwargs)
Parameters:
- index_or_name: The name of the index generated by calling create_index() or ensure_index() method on a collection. If a custom index name was created through thename parameter, then the custom name should be passed here.
- session: This is an optional argument which specifies the ClientSession(from class pymongo.client_session).
- kwargs: These are additional keyword arguments(optional).
What Are Indexes?
Indexes are a special data structure used in MongoDB for increasing the efficiency of query execution. They are defined at the collection level and they allow MongoDB to limit the number of documents that it searches. B-tree data structures are used for indexing in MongoDB. There are various types of Indexes such as single-field indexes, compound indexes, multi-key indexes. For the sake of understanding, in this article, we shall use single-field indexes. On a locally hosted Mongo server, let us create a databasetest with a collectionstudents.
The database will hold the following information about students as follows:
By default, each collection has the_id index. All collections compulsorily have at least one index. If all indexes are removed, then a new index will be automatically generated. We can see the indexes present by running the following command -
Now, we can run the following code to add a new Index called newIndex to the students collection, given that the mongo server is running:
Example 1:Adding an Index to the Collection
Python3importpprintimportpymongo# connectiontry:client=pymongo.MongoClient()db=client['test']print('connection to the server established')exceptException:print('Failed to Connect to server')collection=db.students# creating an indexresp=collection.create_index("newIndex")# printing the auto generated name# returned by MongoDBprint(resp)# index_information() is analogous# to getIndexespprint.pprint(collection.index_information())Output:
As we can see the autogenerated name is newIndex_1.Example 2:Deleting the Index from the Collection
Python3importpprintimportpymongotry:client=pymongo.MongoClient()db=client['test']print('connection to the server established')exceptException:print('Failed to Connect to server')collection=db.students# dropping the index using autogenerated# name from MongoDBcollection.drop_index("newIndex_1")# printing the indexes present on the collectionpprint.pprint(collection.index_information())Output:
The output shows that the newly inserted Index called newIndex was dropped and only the original _id index remained. This is the application of drop_index().
It throws OperationFailure error when trying to drop an index that does not exist.