MongoDB is an open-source document-oriented database. MongoDB stores data in the form of key-value pairs and is a NoSQL database program. The term NoSQL means non-relational.
PyMongo contains tools which are used to interact with the MongoDB database. Now let’s see how to update all the documents in a collection.
Updating all Documents in a Collection
PyMongo includes an update_many() function which updates all the documents which satisfy the given query.
update_many() accepts the following parameters –
- filter – It is the first parameter which is a criteria according to which the documents that satisfy the query are updated.
- update operator- It is the second parameter which contains the information to be updated in the documents.
- upsert- (Optional) It is a boolean. If set to true and there is no document matching the filter, a new document is created.
- array_filters – (Optional) It is an array of filter documents to determine which array elements to modify for an update operation on an array field.
- bypass_document_validation – (Optional) A boolean which skips the document validation when set to True.
- collation – (Optional) specifies the language specific rules for the operation.
- session – (Optional) a ClientSession.
Update Operators in MongoDB
Setting Values:
- $set: Used to set a fields value.
- $setOnInsert: Update value only if a new document insertion.
- $unset: Remove the field and its value.
Numeric Operators:
- $inc: Increases the value by a given amount.
- $min/$max: returns minimum or maximum of value.
- $mul: multiplies the values by a given amount.
Miscellaneous Operators:
- $currentDate: Updates value of a field to current date.
- $rename: Renames a field
Now let’s understand through some examples.
Sample Database:
Some use cases we are going to see in this article where updating many records can be useful:
- Changing or incrementing several elements based on a condition.
- Inserting a new field to multiple or all documents.
Example 1: All the students with marks greater than 35 has been passed.
Python3
from pymongo import MongoClient # Creating an instance of MongoClient # on default localhost # Accessing desired database and collection db = client.gfg collection = db["classroom"] # Update passed field to be true for all # students with marks greater than 35 collection.update_many( {"marks": { "$gt": "35" } }, { "$set": { "passed" : "True" } } ) |
Database After Query:
Example 2: New field called address added to all documents
Python
from pymongo import MongoClient # Creating an instance of MongoClient # on default localhost # Accessing desired database and collection db = client.gfg collection = db["classroom"] # Address filed to be added to all documents collection.update_many( {}, {"$set": { "Address": "value" } }, # don't insert if no document found upsert=False, array_filters=None ) |
Database After query:
