Execution date vs logical date in Apache Airflow - Quick Revision & Key Differences

Recall & Review

beginner

What is the start date in Airflow?

The start date is the timestamp when Airflow schedules a task or DAG to start running. It represents the earliest time the task is eligible to run.

beginner

What does the logical date mean in Airflow?

The logical date is the scheduled time for which the task or DAG run is responsible. It represents the data interval or period the run is processing.

intermediate

How do start date and logical date differ in Airflow?

Start date is when the task is scheduled to run, while logical date is the scheduled time the task run represents. Logical date is often earlier than start date.

intermediate

Why is the logical date important in Airflow scheduling?

Logical date helps Airflow know which data period the task run is processing, enabling correct data partitioning and backfilling.

advanced

If a DAG is scheduled daily at midnight, what would be the logical date and start date for the run at 2024-06-02 00:00?

Logical date: 2024-06-01 00:00 (the data day being processed). Start date: 2024-06-02 00:00 (when the task actually runs).

In Airflow, what does the logical date represent?

A The time the DAG was created

B The actual time the task starts running

C The scheduled time the task run is responsible for

D The time the task finished

Logical date is the scheduled time or data interval the task run processes.

Which date is usually earlier in Airflow: start date or logical date?

A Logical date

B Depends on the DAG

C They are always the same

D Start date

Logical date is usually earlier because it represents the data period before the task runs.

If a DAG runs daily at midnight, what is the logical date for the run at 2024-06-10 00:00?

A 2024-06-09 00:00

B 2024-06-10 00:00

C 2024-06-11 00:00

D The current system time

Logical date is the start of the data interval, so for the run at midnight June 10, it is June 9.

Why does Airflow use logical dates instead of just start dates?

A To log the system time

B To know when the task finished

C To schedule the next run

D To track the data interval the task processes

Logical dates help Airflow manage data intervals and backfills correctly.

Which of these is true about start date in Airflow?

A It is the time the task run is scheduled for

B It is the time the task actually starts running

C It is always earlier than logical date

D It is the time the DAG was last modified

Start date is when the task actually runs, not when it is scheduled.

Explain the difference between start date and logical date in Airflow.

Think about when the task runs versus what data it processes.

Why is understanding logical date important when scheduling DAGs in Airflow?

Consider how Airflow knows which data to work on.