Slim CI with state comparison in dbt - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Slim CI in dbt?

Slim CI is a way to run only the changed models in your dbt project during continuous integration, making tests faster and more efficient.

beginner

How does state comparison help in Slim CI?

State comparison checks the difference between the current project and a previous run to identify which models changed, so only those models and their dependencies run.

intermediate

Which dbt command option enables state comparison for Slim CI?

The --state flag is used with dbt commands to specify the path to the previous run's manifest directory for state comparison.

beginner

What is the benefit of using Slim CI with state comparison in a real project?

It saves time and computing resources by running only the models that changed and their dependencies, instead of the whole project.

beginner

What happens if you run dbt without state comparison in CI?

dbt runs all models every time, which can be slow and use more resources, especially for large projects.

What does the --state flag do in dbt?

A Specifies the previous run's manifest for comparison

B Runs all models regardless of changes

C Deletes old models from the database

D Generates documentation for the project

The --state flag tells dbt where to find the previous run's manifest to compare and find changed models.

Why use Slim CI in dbt?

A To deploy models to production automatically

B To run all models every time

C To skip tests during CI

D To run only changed models and speed up CI

Slim CI focuses on running only changed models to make continuous integration faster and more efficient.

What is required for state comparison to work?

A A saved manifest from a previous dbt run

B A full rebuild of all models

C Manual selection of models to run

D Disabling tests in dbt

State comparison needs a previous manifest file to compare the current project state against.

If no models changed, what does Slim CI do?

A Runs all models

B Runs no models

C Runs only tests

D Fails the CI job

If no changes are detected, Slim CI skips running models to save time.

Which of these is a direct benefit of Slim CI?

A More manual work to select models

B More database storage used

C Reduced CI run time

D Increased chance of errors

Slim CI reduces the time it takes to run CI by focusing only on changed models.

Explain how Slim CI with state comparison works in dbt and why it is useful.

Think about how comparing current and past project states helps decide what to run.

Describe the steps to set up Slim CI with state comparison in a dbt project.

Consider what files and flags are needed to compare states.

Practice

1. What is the main purpose of using --state and --select state:modified in dbt's Slim CI?

easy

A. To delete all previous run artifacts

B. To run all models regardless of changes

C. To create a backup of the current state

D. To run only the models that have changed since the last run

Solution

1. Step 1: Understand the role of --state

   The --state flag points dbt to the previous run's artifacts, allowing comparison between runs.

2. Step 2: Understand --select state:modified

   This selects only the models that have changed compared to the previous state, skipping unchanged models.

3. Final Answer:

   To run only the models that have changed since the last run -> Option D

4. Quick Check:

   Slim CI runs changed models only [OK]

Hint: Slim CI runs changed models only, saving time [OK]

Common Mistakes:

• Thinking it runs all models every time
• Confusing state with backup or deletion
• Assuming it runs unchanged models too

2. Which of the following is the correct syntax to run dbt with Slim CI to select only modified models?

easy

A. dbt run --state path/to/previous --select all

B. dbt run --select state:modified --state path/to/previous

C. dbt run --select modified:state --state=previous_path

D. dbt run --state-modified --select path/to/previous

Solution

1. Step 1: Identify correct flag usage

   The correct flags are --state to specify previous run artifacts and --select state:modified to select changed models.

2. Step 2: Match syntax to flags

   dbt run --select state:modified --state path/to/previous correctly uses --select state:modified and --state path/to/previous in proper order and format.

3. Final Answer:

   dbt run --select state:modified --state path/to/previous -> Option B

4. Quick Check:

   Correct flags and order [OK]

Hint: Use --state then --select state:modified for Slim CI [OK]

Common Mistakes:

• Mixing up flag names or order
• Using incorrect flag syntax
• Selecting all models instead of modified

3. Given the following dbt command run twice with changes in model 'sales':

dbt run --state ./target/run1 --select state:modified
# After modifying 'sales' model
 dbt run --state ./target/run1 --select state:modified

What will the second command do?

medium

A. Run only the 'sales' model because it was modified

B. Run all models again ignoring state

C. Run no models because nothing changed

D. Throw an error due to incorrect state path

Solution

1. Step 1: Understand the first run

   The first command runs all models and saves state in ./target/run1.

2. Step 2: Analyze the second run with modification

   The second command compares current state to ./target/run1 and runs only models that changed, here 'sales'.

3. Final Answer:

   Run only the 'sales' model because it was modified -> Option A

4. Quick Check:

   Modified model runs only [OK]

Hint: Second run runs only changed models using saved state [OK]

Common Mistakes:

• Assuming all models run again
• Thinking no models run if only one changed
• Confusing state path usage

4. You run dbt run --state ./previous_run --select state:modified but get an error saying the state path is invalid. What is the most likely cause?

medium

A. The path './previous_run' does not contain valid dbt run artifacts

B. You forgot to add '--select all' flag

C. The '--state' flag must come after '--select'

D. The command requires '--full-refresh' to work

Solution

1. Step 1: Check the meaning of the error

   An invalid state path error means dbt cannot find or read previous run artifacts at the given path.

2. Step 2: Evaluate other options

   Flags order or missing '--select all' do not cause this error; '--full-refresh' is unrelated.

3. Final Answer:

   The path './previous_run' does not contain valid dbt run artifacts -> Option A

4. Quick Check:

   Invalid state path means missing artifacts [OK]

Hint: Ensure state path has valid previous run artifacts [OK]

Common Mistakes:

• Assuming flag order causes error
• Thinking '--full-refresh' fixes state errors
• Forgetting to generate previous run artifacts

5. You want to optimize your CI pipeline using Slim CI. Your previous run artifacts are stored in ./target/previous. You have models 'A', 'B', and 'C'. Only 'B' was modified. Which command will run only the modified model and also run its dependent models?

hard

A. dbt run --state ./target/previous --select state:modified

B. dbt run --state ./target/previous --select state:modified --full-refresh

C. dbt run --state ./target/previous --select state:modified+

D. dbt run --select state:modified --state ./target/previous --exclude B

Solution

1. Step 1: Understand the '+' operator in selection

   The '+' after state:modified selects modified models plus their dependents.

2. Step 2: Match command to requirement

   dbt run --state ./target/previous --select state:modified+ uses state:modified+ with correct --state path, running 'B' and its dependents.

3. Step 3: Evaluate other options

   dbt run --state ./target/previous --select state:modified runs only modified models without dependents; C adds unnecessary full-refresh; D excludes 'B' incorrectly.

4. Final Answer:

   dbt run --state ./target/previous --select state:modified+ -> Option C

5. Quick Check:

   Modified plus dependents run [OK]

Hint: Add '+' to include dependents of modified models [OK]

Common Mistakes:

• Not including dependents with '+'
• Using --full-refresh unnecessarily
• Excluding modified models by mistake