Python MongoDB - Update_many Query

Python MongoDB – Update_many Query

Last Updated : 26 May, 2020

MongoDB is a NoSQL database management system. Unlike MySQL the data in MongoDB is not stored as relations or tables. Data in mongoDB is stored as documents. Documents are Javascript/JSON like objects. More formally documents in MongoDB use BSON. PyMongo is a MongoDB API for python. It allows to read and write data from a MongoDB database using a python script. It needs both python and mongoDB to be installed on the system.

Update_many()

Update function has been deprecated in newer versions of MongoDB (3.xx and above). Earlier update function could be used for both single updates and multiple using “multi = true”. But in newer versions of mongoDB it is recommended to use update_many() and update_one().

The major difference is that the user needs to plan ahead if the query is going to be updating single or multiple documents.

Syntax:

db.collection.updateMany(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>
   }
)

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

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 
client = MongoClient('mongodb://localhost:27017') 
  
# 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 
client = MongoClient('mongodb://localhost:27017') 
  
# 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
   ) 