PR review workflows for dbt changes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Key Step in PR Review Workflow for dbt Model Changes

In a typical PR review workflow for dbt model changes, which step ensures that the new or modified models do not break existing data transformations?

A Merging the PR directly without any checks

B Running dbt tests and validations on the changed models

C Deleting the existing models before merging

D Ignoring the PR and continuing development

💡 Hint

Think about how to verify that changes are safe before merging.

Running dbt tests and validations helps catch errors or issues introduced by changes, ensuring data integrity before merging.

❓ Predict Output

intermediate

Output of dbt run in PR Workflow

What is the expected output when running dbt run during a PR review for a model that has no syntax errors and passes all dependencies?

dbt

dbt run

A All models run successfully with status 'OK' and no errors

B Syntax errors reported and run aborted

C Partial models run with some failures

D No output is shown

💡 Hint

Consider what happens when dbt runs models without issues.

If the models have no syntax errors and dependencies are met, dbt run completes successfully with all models marked as 'OK'.

🔧 Debug

advanced

Identifying the Cause of a Failed dbt Test in PR Review

During a PR review, a dbt test fails with the error: unique key violation. What is the most likely cause?

A The test syntax is incorrect

B The dbt project configuration file is missing

C The database connection is lost

D The model contains duplicate values in a column that should be unique

💡 Hint

Think about what a unique key violation means in data.

A unique key violation means the data has duplicates in a column that is expected to have unique values, causing the test to fail.

🚀 Application

advanced

Best Practice for Handling Schema Changes in PR Workflow

When a PR includes schema changes like adding a new column to a dbt model, what is the best practice to ensure smooth deployment?

A Add the new column in the model and update tests and documentation accordingly before merging

B Merge the PR without updating tests or documentation

C Delete the old model and create a new one with the new schema

D Ignore schema changes and only update SQL logic

💡 Hint

Think about maintaining quality and clarity in your dbt project.

Updating tests and documentation ensures the new schema is validated and clearly understood, preventing issues after deployment.

❓ visualization

expert

Interpreting a dbt DAG Graph in PR Review

You see a DAG graph generated by dbt during a PR review. The graph shows a model with multiple upstream dependencies and several downstream models. What does this imply about the impact of changes to this model?

A Changes to this model only affect itself and no other models

B This model has no dependencies and is isolated

C Changes to this model can affect many other models both upstream and downstream

D The graph is incorrect and should be ignored

💡 Hint

Consider what upstream and downstream dependencies mean in a DAG.

A model with many upstream and downstream dependencies means changes can ripple through the project, affecting many models.

Practice

1. What is the main purpose of using a PR (Pull Request) review workflow in dbt projects?

easy

A. To ensure changes are reviewed and tested before merging

B. To speed up merging without checks

C. To delete old branches automatically

D. To create new dbt models without review

Solution

1. Step 1: Understand PR review workflow purpose

   PR review workflows are designed to check code changes carefully before they become part of the main project.

2. Step 2: Identify the correct purpose in dbt context

   In dbt, this means reviewing and testing data models to avoid errors and keep the project reliable.

3. Final Answer:

   To ensure changes are reviewed and tested before merging -> Option A

4. Quick Check:

   PR review = review and test before merge [OK]

Hint: PR reviews catch errors before merging [OK]

Common Mistakes:

• Thinking PRs speed up merging without checks
• Confusing PR reviews with branch deletion
• Assuming PRs create models automatically

2. Which of the following is the correct syntax to create a new branch for a dbt PR workflow using Git?

easy

A. git branch new-feature

B. git merge new-feature

C. git push new-feature

D. git checkout -b new-feature

Solution

1. Step 1: Understand Git branch creation commands

   To create and switch to a new branch in one step, use git checkout -b branch-name.

2. Step 2: Identify the correct command for new branch creation

   git checkout -b new-feature uses git checkout -b new-feature, which creates and switches to the branch.

3. Final Answer:

   git checkout -b new-feature -> Option D

4. Quick Check:

   New branch creation = git checkout -b [OK]

Hint: Use git checkout -b to create and switch branch [OK]

Common Mistakes:

• Using git branch without switching
• Confusing merge with branch creation
• Trying to push before creating branch

3. Given this simplified dbt test command in a PR workflow:

dbt test --models my_model

What will happen if the model my_model has a failing test?

medium

A. The command deletes the model automatically

B. The command completes successfully with no error

C. The command fails and returns a non-zero exit code

D. The command ignores the test and continues

Solution

1. Step 1: Understand dbt test behavior

   When a dbt test fails, the command returns a non-zero exit code indicating failure.

2. Step 2: Identify the effect of a failing test in PR workflow

   This failure stops the PR from merging until the issue is fixed.

3. Final Answer:

   The command fails and returns a non-zero exit code -> Option C

4. Quick Check:

   Failing test = command fails with error code [OK]

Hint: Failing dbt tests cause command to fail [OK]

Common Mistakes:

• Assuming tests pass silently
• Thinking dbt deletes models on failure
• Believing tests are ignored automatically

4. You wrote a dbt model and created a PR, but the automated tests fail. Which of the following is the best way to debug the issue?

medium

A. Ignore the test failures and merge the PR

B. Check the test logs and fix the model SQL accordingly

C. Delete the model file and close the PR

D. Merge the PR and fix errors later in production

Solution

1. Step 1: Understand the role of test logs in debugging

   Test logs show which tests failed and why, helping identify SQL errors or data issues.

2. Step 2: Choose the correct debugging approach

   Fixing the model SQL based on logs ensures the PR passes tests before merging.

3. Final Answer:

   Check the test logs and fix the model SQL accordingly -> Option B

4. Quick Check:

   Debug by reviewing logs and fixing code [OK]

Hint: Use test logs to find and fix errors [OK]

Common Mistakes:

• Ignoring test failures
• Deleting models unnecessarily
• Merging broken code into main branch

5. In a team using dbt with PR review workflows, which combination of practices best ensures data model quality before merging?

hard

A. Create feature branches, run automated tests, and require team approval

B. Directly commit to main branch and run tests after merging

C. Skip tests and rely on manual checks only

D. Merge PRs without reviews to speed up deployment

Solution

1. Step 1: Identify best practices in PR workflows

   Using feature branches isolates changes, automated tests catch errors early, and team approval ensures quality review.

2. Step 2: Compare options to find the best combination

   Create feature branches, run automated tests, and require team approval includes all these practices, while others skip important steps or risk errors.

3. Final Answer:

   Create feature branches, run automated tests, and require team approval -> Option A

4. Quick Check:

   Branch + tests + review = quality assurance [OK]

Hint: Combine branches, tests, and reviews for quality [OK]

Common Mistakes:

• Committing directly to main branch
• Skipping automated tests
• Merging without team review