Difference Between findAndModify and Update in MongoDB?

MongoDB, with its flexible document-based data model, offers a range of methods for updating data within collections. Two of the most commonly used methods, findAndModify and update, each has its unique strengths and purposes. Understanding the differences between these methods can significantly impact the efficiency and effectiveness of our MongoDB operations. Let's understand what is findAndModify and update along with their syntax, examples and so on.

What is the findAndModify() Method?

• findAndModify() is a MongoDB method that allows us to search for a specific document in a collection, update it based on certain conditions (if found), and return the modified document or, if no documents are found, insert a new document instead.
  
• It takes a filter query, sort order, update document, etc as parameters to find and modify the document atomically.
  
• By default, it returns the document as it was BEFORE the update. To return the updated document, we need to set the new option to true.
  
• It locks the document during the operation to ensure no other operations modify it during the findAndModify.
  
• Use it when we need to atomically read, update, and return a document in a single go.

Syntax:

db.collection.findAndModify(
<query>,
<sort>,
<update>,
<options>
)

Explanation:

• query - Filter query to find the document.
  
• sort - Optional sort order for the query.
  
• update - Update operations to perform on the document.
  
• options - Additional options like new, remove, etc

Example of findAndModify() Method

Suppose we have a gfg database in courses collection which stores information about various courses. Each document in the collection represents a course and contains details such as the course name, Instructore name, fees and duration.

After inserting record into the courses collection, Our courses looks like:

Example 1: Let's Find the Fees of Java Course to 25000 Otherwise Modified it

Here, we are modifying the value of field Fees of the Java course from 12000 to 25000 using the findAndModify method.

db.courses.findAndModify({
  query: { Course: 'Java' },
  update: { $set: { Fees: "25000" } }
});

Output:

Note: findAndModify() method is deprecated in MongoDB starting from the 3.6 version.

Example 2: Let's Find the Instructor of Python to Shree Otherwise Modified it

Here, we are modifying the value of field Instructor of the Python course from Shreya to Shree using the findAndModify method.

db.courses.findAndModify({
  query: { Course: 'Python' },
  update: { $set: { Instructor: 'Shree' } },
  new: true
});

Output:

What is the update() Method?

• update() is a simpler command that updates documents in a collection based on a query. It does not return the modified document, only the number of matching documents updated.
  
• It takes a filter object to match the documents to update and an update object with the changes.
  
• By default it will update a single document, set multi to true to update multiple.
  
• Returns a WriteResult object with info about the operation.
  
• Can use operators like $set, $inc to update specific fields atomically.

Syntax:

db.collection.update(
   <filter>,
   <update>,
   <options>
)

Explanation:

• filter: Specifies criteria to match documents to update.
  
• update: Specifies update operations to perform.
  
• options: Additional options like new, remove, etc

Example of update() Method

Example 1: Update the Fees of Java Course to 25000

Here, we are modifying the value of field Fees of the Java course from 12000 to 25000 using the update method.

db.courses.update(
  { Course: 'Java' },
  { $set: { Fees: "25000" } }
);

Output:

Example 2: Update the Instructor of Python to Shree

Here, we are modifying the value of field Instructor of the Python course from Shreya to Shree using the update method.

db.courses.update(
  { Course: 'Python' },
  { $set: { Instructor: 'Shree' } }
);

Output:

Conclusion

Overall, MongoDB provides the findAndModify and update methods for updating data within collections, each with its own strengths and use cases. findAndModify is ideal for atomic operations where you need to read, update, and return a document in a single operation, while update is simpler and used for updating documents based on a query without returning the modified document.