Bulk write operations in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a bulk write operation in MongoDB?

A bulk write operation allows you to perform multiple write actions (like insert, update, delete) in a single request to the database, improving efficiency and reducing network overhead.

beginner

Name two types of bulk write operations in MongoDB.

The two types are ordered and unordered bulk operations. Ordered operations stop on the first error, unordered continue despite errors.

beginner

What method is used in MongoDB to perform bulk write operations?

The bulkWrite() method is used on a collection to perform multiple write operations in bulk.

intermediate

How do unordered bulk operations behave when an error occurs?

Unordered bulk operations continue executing the remaining operations even if some operations fail, allowing partial success.

beginner

Give an example of a write operation you can include in a bulkWrite array.

Examples include { insertOne: { document: {...} } }, { updateOne: { filter: {...}, update: {...} } }, and { deleteOne: { filter: {...} } }.

Which MongoDB method allows multiple write operations in one call?

A bulkWrite()

B insertMany()

C updateOne()

D find()

The bulkWrite() method lets you perform many write operations like insert, update, and delete in a single request.

What happens in an ordered bulk operation if one operation fails?

A The operation retries automatically

B All operations continue regardless

C Only the failed operation is skipped

D The bulk operation stops immediately

In ordered bulk operations, if one operation fails, the process stops and no further operations run.

Which of these is NOT a valid bulk write operation in MongoDB?

A insertOne

B deleteOne

C findOne

D updateMany

findOne is a read operation, not a write operation, so it cannot be used in bulkWrite.

Unordered bulk operations are useful when:

A You want to stop on first error

B You want to continue despite errors

C You only have one operation

D You want to read data

Unordered bulk operations continue executing all operations even if some fail.

Which option correctly describes bulkWrite's input?

A An array of write operation objects

B A query filter

C A single document

D A connection string

bulkWrite takes an array of objects, each describing a write operation like insertOne or updateOne.

Explain what bulk write operations are in MongoDB and why they are useful.

Think about doing many tasks at once instead of one by one.

Describe the difference between ordered and unordered bulk write operations.

Consider how errors affect the flow of operations.

Practice

1. What is the main advantage of using bulkWrite() in MongoDB?

easy

A. It allows multiple write operations in a single request, improving performance.

B. It automatically backs up the database before each write.

C. It only works with read operations.

D. It requires separate calls for each write operation.

Solution

1. Step 1: Understand what bulkWrite() does

   bulkWrite() lets you send many write commands (insert, update, delete) in one call.

2. Step 2: Identify the benefit

   Sending many operations at once reduces network overhead and speeds up database changes.

3. Final Answer:

   It allows multiple write operations in a single request, improving performance. -> Option A

4. Quick Check:

   Bulk write = multiple writes in one call [OK]

Hint: Bulk write = many writes at once for speed [OK]

Common Mistakes:

• Thinking bulkWrite only reads data
• Believing it backs up data automatically
• Assuming it requires separate calls per operation

2. Which of the following is the correct syntax to perform a bulk write with an insert and an update in MongoDB?

easy

A. db.collection.bulkWrite([{ insertOne: { document: { name: 'Alice' } } }, { updateOne: { filter: { name: 'Bob' }, update: { $set: { age: 30 } } } }])

B. db.collection.bulkWrite(insertOne: { document: { name: 'Alice' } }, updateOne: { filter: { name: 'Bob' }, update: { $set: { age: 30 } } })

C. db.collection.bulkWrite([{ insert: { name: 'Alice' } }, { update: { name: 'Bob', age: 30 } }])

D. db.collection.bulkWrite([{ insertOne: { name: 'Alice' } }, { updateOne: { name: 'Bob', age: 30 } }])

Solution

1. Step 1: Check the bulkWrite syntax

   bulkWrite expects an array of operation objects like { insertOne: { document: {...} } } or { updateOne: { filter: {...}, update: {...} } }.

2. Step 2: Match options to syntax

   db.collection.bulkWrite([{ insertOne: { document: { name: 'Alice' } } }, { updateOne: { filter: { name: 'Bob' }, update: { $set: { age: 30 } } } }]) correctly uses insertOne and updateOne with proper nested objects. Others miss brackets or use wrong keys.

3. Final Answer:

   db.collection.bulkWrite([{ insertOne: { document: { name: 'Alice' } } }, { updateOne: { filter: { name: 'Bob' }, update: { $set: { age: 30 } } } }]) -> Option A

4. Quick Check:

   Correct bulkWrite syntax = db.collection.bulkWrite([{ insertOne: { document: { name: 'Alice' } } }, { updateOne: { filter: { name: 'Bob' }, update: { $set: { age: 30 } } } }]) [OK]

Hint: bulkWrite needs array of operation objects [OK]

Common Mistakes:

• Omitting the array brackets []
• Using wrong keys like 'insert' instead of 'insertOne'
• Not nesting filter and update properly

3. Given the following bulkWrite operation, what will be the result in the collection?

db.users.bulkWrite([
  { insertOne: { document: { _id: 1, name: 'John' } } },
  { updateOne: { filter: { _id: 1 }, update: { $set: { age: 25 } } } },
  { deleteOne: { filter: { name: 'John' } } }
])

medium

A. The collection will have one document: { _id: 1, name: 'John', age: 25 }

B. The operation will fail due to conflicting commands.

C. The collection will be empty after the operations.

D. The collection will have one document: { _id: 1, name: 'John' } without age.

Solution

1. Step 1: Analyze each bulkWrite operation in order

   First, insert { _id: 1, name: 'John' }. Second, update that document to add age: 25. Third, delete the document where name is 'John'.

2. Step 2: Determine final collection state

   After deletion, the document is removed, so the collection is empty.

3. Final Answer:

   The collection will be empty after the operations. -> Option C

4. Quick Check:

   Insert + update + delete = empty collection [OK]

Hint: Last delete removes the document, leaving collection empty [OK]

Common Mistakes:

• Assuming update adds a new document
• Ignoring the delete operation
• Thinking operations run independently

4. Identify the error in this bulkWrite operation:

db.products.bulkWrite([
  { insertOne: { document: { _id: 101, name: 'Pen', price: 10 } } },
  { updateOne: { filter: { _id: 101 }, update: { name: 'Pencil' } } }
])

medium

A. The filter in updateOne is incorrect.

B. The insertOne operation is missing the document key.

C. bulkWrite cannot mix insertOne and updateOne operations.

D. The update document is missing the $set operator.

Solution

1. Step 1: Review the updateOne operation

   The update document must use an update operator like $set to modify fields.

2. Step 2: Identify the missing operator

   Here, { name: 'Pencil' } is used directly, which replaces the entire document (losing the price field). It should be { $set: { name: 'Pencil' } }.

3. Final Answer:

   The update document is missing the $set operator. -> Option D

4. Quick Check:

   Update needs $set for field changes [OK]

Hint: Always use $set in update documents [OK]

Common Mistakes:

• Forgetting $set in updateOne
• Thinking insertOne needs $set
• Believing bulkWrite can't mix operations

5. You want to update multiple documents in a collection using bulkWrite(). You have these operations:

• Update user with _id 1 to set age to 30
• Update user with _id 2 to set age to 25
• Insert a new user with _id 3 and name 'Anna'

Which bulkWrite array correctly performs all these changes in one call?

hard

A. [
{ updateMany: { filter: { _id: { $in: [1, 2] } }, update: { $set: { age: 30 } } } },
{ insertOne: { document: { _id: 3, name: 'Anna' } } }
]

B. [
{ updateOne: { filter: { _id: 1 }, update: { $set: { age: 30 } } } },
{ updateOne: { filter: { _id: 2 }, update: { $set: { age: 25 } } } },
{ insertOne: { document: { _id: 3, name: 'Anna' } } }
]

C. [
{ updateOne: { filter: { _id: 1 }, update: { age: 30 } } },
{ updateOne: { filter: { _id: 2 }, update: { age: 25 } } },
{ insertOne: { document: { _id: 3, name: 'Anna' } } }
]

D. [
{ updateOne: { filter: { _id: 1 }, update: { $set: { age: 30 } } } },
{ updateOne: { filter: { _id: 2 }, update: { $set: { age: 25 } } } },
{ insertOne: { document: { name: 'Anna' } } }
]

Solution

1. Step 1: Check each updateOne operation

   Both updates correctly use updateOne with $set to change age for _id 1 and 2.

2. Step 2: Verify insertOne operation

   [ { updateOne: { filter: { _id: 1 }, update: { $set: { age: 30 } } } }, { updateOne: { filter: { _id: 2 }, update: { $set: { age: 25 } } } }, { insertOne: { document: { _id: 3, name: 'Anna' } } } ] inserts a new document with _id 3 and name 'Anna', which matches the requirement.

3. Step 3: Compare with other options

   [ { updateMany: { filter: { _id: { $in: [1, 2] } }, update: { $set: { age: 30 } } } }, { insertOne: { document: { _id: 3, name: 'Anna' } } } ] uses updateMany incorrectly (age 30 for both, but second should be 25). [ { updateOne: { filter: { _id: 1 }, update: { age: 30 } } }, { updateOne: { filter: { _id: 2 }, update: { age: 25 } } }, { insertOne: { document: { _id: 3, name: 'Anna' } } } ] misses $set. [ { updateOne: { filter: { _id: 1 }, update: { $set: { age: 30 } } } }, { updateOne: { filter: { _id: 2 }, update: { $set: { age: 25 } } } }, { insertOne: { document: { name: 'Anna' } } } ] misses _id in insert.

4. Final Answer:

   [ { updateOne: { filter: { _id: 1 }, update: { $set: { age: 30 } } } }, { updateOne: { filter: { _id: 2 }, update: { $set: { age: 25 } } } }, { insertOne: { document: { _id: 3, name: 'Anna' } } } ] -> Option B

5. Quick Check:

   Use updateOne with $set and insertOne with full document [OK]

Hint: Use updateOne with $set and insertOne with full document [OK]

Common Mistakes:

• Using update without $set
• Missing _id in insert document
• Using updateMany when individual updates differ