Alembic migrations in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new Alembic migration revision.

FastAPI

alembic [1] -m "add new table"

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

Arevision

Bupgrade

Cdowngrade

Dinit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upgrade' instead of 'revision' to create migration.

The revision command creates a new migration file with a message describing the change.

2fill in blank

medium

Complete the code to apply all pending Alembic migrations to the database.

FastAPI

alembic [1] head

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

Adowngrade

Brevision

Cupgrade

Dcurrent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'revision' instead of 'upgrade' to apply migrations.

The upgrade head command applies all migrations up to the latest.

3fill in blank

hard

Fix the error in the Alembic command to revert the last migration.

FastAPI

alembic [1] -1

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

Adowngrade

Brevision

Cupgrade

Dhistory

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upgrade' instead of 'downgrade' to revert migrations.

The downgrade -1 command reverts the last migration applied.

4fill in blank

hard

Fill both blanks to generate an Alembic migration that autogenerates changes and names it.

FastAPI

alembic [1] -m "[2]" --autogenerate

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

Arevision

Bupgrade

Cdowngrade

Dinit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upgrade' instead of 'revision' to create migration.

The revision command with --autogenerate creates a migration file automatically detecting changes. The -m flag names the migration.

5fill in blank

hard

Fill all three blanks to write a Python Alembic migration script that adds a new column.

FastAPI

def upgrade():
    op.add_column('[1]', sa.Column('[2]', sa.String(), nullable=[3]))

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

Ausers

Bemail

CFalse

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Setting nullable to True when the column should not allow nulls.

This migration adds a new column named email of type String to the users table. The column is set to not allow null values (nullable=False).

Practice

1. What is the main purpose of Alembic migrations in a FastAPI project?

easy

A. To manage and apply database schema changes safely over time

B. To handle HTTP requests and responses

C. To serve static files like images and CSS

D. To create user interface components

Solution

1. Step 1: Understand Alembic's role

   Alembic is a tool designed to manage database schema changes, not web server tasks.

2. Step 2: Identify the correct purpose

   It helps developers apply, track, and revert database changes safely during development and deployment.

3. Final Answer:

   To manage and apply database schema changes safely over time -> Option A

4. Quick Check:

   Alembic = database migrations [OK]

Hint: Alembic is for database schema changes, not web or UI tasks [OK]

Common Mistakes:

• Confusing Alembic with FastAPI routing
• Thinking Alembic serves static files
• Assuming Alembic builds UI components

2. Which Alembic command creates a new migration script file?

easy

A. alembic upgrade head

B. alembic init migrations

C. alembic downgrade -1

D. alembic revision -m "message"

Solution

1. Step 1: Identify commands for migration scripts

   The command to create a new migration script is revision with a message describing the change.

2. Step 2: Match the command

   alembic revision -m "message" creates a new migration file with the given message.

3. Final Answer:

   alembic revision -m "message" -> Option D

4. Quick Check:

   revision = create migration script [OK]

Hint: Use 'revision' with -m to create migration scripts [OK]

Common Mistakes:

• Using 'upgrade' to create scripts instead of apply them
• Confusing 'downgrade' with script creation
• Using 'init' after project setup

3. Given this Alembic command sequence:
alembic revision -m "add users table"
alembic upgrade head
What happens after running these commands?

medium

A. The database schema is reset to the initial state

B. The migration script is deleted and no changes are applied

C. A new migration script is created and the database schema is updated to include the users table

D. The database schema is downgraded by one version

Solution

1. Step 1: Understand the revision command

   alembic revision -m "add users table" creates a new migration script file describing the addition of the users table.

2. Step 2: Understand the upgrade command

   alembic upgrade head applies all migrations up to the latest, updating the database schema accordingly.

3. Final Answer:

   A new migration script is created and the database schema is updated to include the users table -> Option C

4. Quick Check:

   revision + upgrade = new migration applied [OK]

Hint: Revision creates script; upgrade applies it to DB [OK]

Common Mistakes:

• Thinking upgrade resets or deletes migrations
• Confusing downgrade with upgrade
• Assuming revision applies changes immediately

4. You run alembic upgrade head but get an error about missing dependencies in your migration script. What is the best way to fix this?

medium

A. Edit the migration script to add missing imports or fix syntax errors

B. Delete all migration scripts and start over

C. Run alembic downgrade base without fixing scripts

D. Ignore the error and rerun the command

Solution

1. Step 1: Identify cause of error

   Missing dependencies or syntax errors in migration scripts cause upgrade failures.

2. Step 2: Fix the migration script

   Editing the script to add missing imports or correct syntax resolves the error and allows upgrade to succeed.

3. Final Answer:

   Edit the migration script to add missing imports or fix syntax errors -> Option A

4. Quick Check:

   Fix script errors before upgrading [OK]

Hint: Fix migration script errors before upgrading [OK]

Common Mistakes:

• Deleting scripts unnecessarily
• Ignoring errors and retrying blindly
• Downgrading without fixing root cause

5. You want to add a new column to an existing table using Alembic migrations. Which sequence correctly applies this change without losing existing data?

hard

A. Delete the database and recreate it with the new column

B. Create a new revision script adding the column, then run alembic upgrade head

C. Modify the existing migration script that created the table and rerun alembic upgrade head

D. Run alembic downgrade base then create a new revision script

Solution

1. Step 1: Create a new migration script

   Adding a new column requires a new migration script describing the change to preserve history and data.

2. Step 2: Apply the migration

   Running alembic upgrade head applies the new migration safely without deleting existing data.

3. Final Answer:

   Create a new revision script adding the column, then run alembic upgrade head -> Option B

4. Quick Check:

   New revision + upgrade = safe schema update [OK]

Hint: Always create new revision for schema changes, then upgrade [OK]

Common Mistakes:

• Modifying old migration scripts after applying
• Deleting database instead of migrating
• Downgrading unnecessarily before adding columns