Transactions in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a transaction using TypeORM's QueryRunner.

NestJS

const queryRunner = dataSource.createQueryRunner();
await queryRunner.connect();
await queryRunner.[1]();

Drag options to blanks, or click blank then click option'

AstartTransaction

BcommitTransaction

CrollbackTransaction

Drelease

Attempts:

3 left

💡 Hint

Common Mistakes

Using commitTransaction instead of startTransaction

Calling release before starting the transaction

To begin a transaction, you use startTransaction() on the QueryRunner.

2fill in blank

medium

Complete the code to commit the transaction after successful operations.

NestJS

try {
  // some database operations
  await queryRunner.[1]();
} catch (error) {
  await queryRunner.rollbackTransaction();
}

Drag options to blanks, or click blank then click option'

AstartTransaction

BcommitTransaction

Crelease

Dconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Calling startTransaction again instead of commitTransaction

Forgetting to commit and only rolling back

After successful operations, you commit the transaction using commitTransaction().

3fill in blank

hard

Fix the error in the transaction cleanup by completing the code to release the QueryRunner.

NestJS

finally {
  await queryRunner.[1]();
}

Drag options to blanks, or click blank then click option'

Arelease

BrollbackTransaction

CcommitTransaction

DstartTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Calling commitTransaction or rollbackTransaction in finally block

Not releasing the QueryRunner causing connection leaks

After finishing the transaction, always release the QueryRunner with release() to free resources.

4fill in blank

hard

Fill both blanks to create a transaction that rolls back on error and releases the QueryRunner.

NestJS

try {
  await queryRunner.startTransaction();
  // operations
  await queryRunner.commitTransaction();
} catch (error) {
  await queryRunner.[1]();
} finally {
  await queryRunner.[2]();
}

Drag options to blanks, or click blank then click option'

ArollbackTransaction

Brelease

CstartTransaction

DcommitTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping rollback and release methods

Forgetting to release the QueryRunner

On error, rollback the transaction with rollbackTransaction(), then always release the QueryRunner with release().

5fill in blank

hard

Fill all three blanks to create an object that maps entity names to their repository instances inside a transaction.

NestJS

const repositories = {
  [1]: queryRunner.manager.getRepository([2]),
  [3]: queryRunner.manager.getRepository(ProductEntity),
};

Drag options to blanks, or click blank then click option'

A"userEntity"

BUserEntity

C"productEntity"

DProductEntity

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys or quoted class names

Mixing keys and values incorrectly

Keys are strings like "userEntity" and "productEntity", values are entity classes like UserEntity and ProductEntity.