Slim CI with state comparison in dbt - Step-by-Step Execution

Concept Flow - Slim CI with state comparison

Start: Trigger CI

↓

Fetch current state

↓

Fetch previous state

↓

Compare states

↓

Run only [Skip run

↓

Report results

↓

End

The CI process fetches current and previous states, compares them, runs only changed models if any, otherwise skips, then reports results.

Execution Sample

dbt

dbt run --state ./target
# Compares current models with previous run
# Runs only changed models

This command runs dbt models selectively by comparing current state with previous state to speed up CI.

Execution Table

Step	Action	Current State	Previous State	Comparison Result	CI Action
1	Fetch current state	models: A, B, C	N/A	N/A	Prepare for comparison
2	Fetch previous state	models: A, B, C	models: A, B, C	N/A	Ready to compare
3	Compare states	models: A, B, C	models: A, B, C	No changes detected	Skip model runs
4	Report results	N/A	N/A	No models run	CI passes quickly

💡 No changes detected, so CI skips running models to save time.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
current_state	empty	models: A, B, C	models: A, B, C	models: A, B, C	models: A, B, C
previous_state	empty	empty	models: A, B, C	models: A, B, C	models: A, B, C
comparison_result	none	none	none	no changes	no changes
ci_action	none	none	none	skip runs	skip runs

Key Moments - 2 Insights

Why does the CI skip running models even though the command 'dbt run' was executed?

Because the comparison_result in the execution_table at step 3 shows 'No changes detected', so the CI action is to skip running models to save time.

What happens if the previous state is missing or empty?

If previous_state is empty, the comparison cannot detect changes, so CI will run all models by default to ensure correctness.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the comparison result?

A No changes detected

B Models A and B changed

C Previous state missing

D All models changed

💡 Hint

Check the 'Comparison Result' column in row 3 of the execution_table.

At which step does the CI decide to skip running models?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'CI Action' column in the execution_table to find when 'skip runs' happens.

If a model changed between states, how would the CI action change in the table?

A CI would skip running models

B CI would run only changed models

C CI would run no models

D CI would run all models regardless

💡 Hint

Refer to the concept_flow where changed models trigger running only those models.

Concept Snapshot

Slim CI with state comparison:
- Fetch current and previous states
- Compare models for changes
- Run only changed models if any
- Skip runs if no changes
- Saves CI time and resources

Full Transcript

Slim CI with state comparison is a process where the continuous integration system fetches the current state of dbt models and compares it with the previous state. If no changes are detected, the CI skips running models to save time. If changes exist, only those changed models run. This approach speeds up CI by avoiding unnecessary runs. The execution table shows steps from fetching states, comparing, deciding CI action, and reporting results. Variables track the states and decisions. Key moments clarify why skipping happens and what if previous state is missing. The quiz tests understanding of comparison results, decision steps, and CI actions based on changes.