Overview:
- A MongoDB collection consists of several JSON documents in binary format.
- To delete records from a MongoDB collection, the PyMongo Python driver offers several variants of delete operation through the methods
- delete_one()
- delete_many()
Delete one document satisfying a filter condition:
- To delete only one document, that meets the specified filter conditionamong several others, the method can be called on a object.
- The example below specifies the condition for the single document that is to be deleted is {"red" : 123, "green" : 223}.
Example:
|
# import the python driver for MongoDB from pymongo import MongoClient
# Create a MongoDB client mongoDBConnection = MongoClient('mongodb://localhost:27017/')
# Get a collection instance database = mongoDBConnection.sample collection = database.sample1
# Print the collection before deleting a single record meeting the criteria print("Before deletion:"); for mongoDBdocument in collection.find(): print(mongoDBdocument)
# Delete one record satisfying the filter condition deleteResult = collection.delete_one({"red" : 123, "green" : 223})
print("Number of documents deleted from the MongoDB collection:") print(deleteResult.deleted_count)
# Print the collection after deleting a single record meeting the criteria print("After deletion:"); for mongoDBdocument in collection.find(): print(mongoDBdocument) |
Output:
|
Before deletion: {'_id': ObjectId('5ab9fad002334a0303b029c1'), 'color1': 'red', 'color2': 'blue'} {'_id': ObjectId('5ab9fb8302334a031cc2fc14'), 'red': 146, 'green': 46, 'blue': 246} {'_id': ObjectId('5aba309f74d9af6fff2f2209'), 'red': 123.0, 'green': 223.0, 'blue': 23.0} Number of documents deleted from the MongoDB collection: 1 After deletion: {'_id': ObjectId('5ab9fad002334a0303b029c1'), 'color1': 'red', 'color2': 'blue'} {'_id': ObjectId('5ab9fb8302334a031cc2fc14'), 'red': 146, 'green': 46, 'blue': 246} |
Deleting multiple documents satisfying a filter condition:
- To delete multiple documents from a MongoDB collection the db.collection.deletemany()method can be used.
- db.collection.deletemany()can be passed with a JSON document specifying the filter condition. This method removes all the documents matching the specified filter condition.
- If the filter condition is empty the method db.collection.deletemany()removes all the documents from the document collection.
Example:
|
# import the python driver for MongoDB from pymongo import MongoClient
# Create a MongoDB client mongoDBConnection = MongoClient('localhost', 27017)
# Get a collection instance collection = mongoDBConnection.sample.orders
# Print the collection before deleting a single record meeting the criteria print("Before deletion:"); for mongoDBdocument in collection.find(): print(mongoDBdocument)
# Delete all the order records which are in cancelled state deleteResult = collection.delete_many({"Status" : "Cancelled"})
print("Number of documents deleted from the MongoDB collection:") print(deleteResult.deleted_count)
# Print the collection after deleting a single record meeting the criteria print("After deletion:"); for mongoDBdocument in collection.find(): print(mongoDBdocument) |
Output:
|
Before deletion: {'_id': ObjectId('5aba593174d9af6fff2f2213'), 'OrderId': '536728', 'Symbol': 'MSFT', 'Side': 'Buy', 'Qty': '100', 'Price': '91.95', 'Venue': 'NasdaqGS', 'Status': 'Ordered', 'TimeStamp': '1522161353'} {'_id': ObjectId('5aba596374d9af6fff2f2216'), 'OrderId': '536821', 'Symbol': 'GOOG', 'Side': 'Sell', 'Qty': '50', 'Price': '1147.01', 'Venue': 'NasdaqGS', 'Status': 'Cancelled', 'TimeStamp': '1522161363'} {'_id': ObjectId('5aba597274d9af6fff2f2217'), 'OrderId': '536841', 'Symbol': 'AMZN', 'Side': 'Sell', 'Qty': '50', 'Price': '1668.87', 'Venue': 'NasdaqGS', 'Status': 'Cancelled', 'TimeStamp': '1522161461'} Number of documents deleted from the MongoDB collection: 2 After deletion: {'_id': ObjectId('5aba593174d9af6fff2f2213'), 'OrderId': '536728', 'Symbol': 'MSFT', 'Side': 'Buy', 'Qty': '100', 'Price': '91.95', 'Venue': 'NasdaqGS', 'Status': 'Ordered', 'TimeStamp': '1522161353'} |