Databricks Data Engineer Associate Question 360
Select 2A data engineer is tasked with loading data from a cloud storage location into a Delta table using the COPY INTO command in Databricks. The data engineer must ensure that duplicate records are not inserted into the target Delta table. Which of the following approaches will help the data engineer achieve this goal?
- A
Use the COPY INTO command with the 'MERGE INTO' clause to check for duplicates.
- B
Ensure that the source files have deterministic filenames and use the 'COPY INTO' command with the 'FILE FORMAT' option.
- C
Use the COPY INTO command and specify the 'OVERWRITE' option to replace existing data.
- D
Load the data using the COPY INTO command and add a 'WHERE NOT EXISTS' condition to the target table.
- E
Implement a uniqueness constraint at the Delta table level and then use the COPY INTO command.
Show answer and explanation
Correct answers: B, E
Explanation
To prevent duplicate records when using COPY INTO, it is crucial to ensure that the source files are not reprocessed unnecessarily, which can be achieved through deterministic filenames. Additionally, Delta tables can enforce uniqueness constraints to avoid duplicate rows at the table level. COPY INTO does not natively support complex filtering logic or merging, so these tasks must be implemented using other Delta Lake features or commands.
- A. Incorrect.
The COPY INTO command does not support a 'MERGE INTO' clause directly. MERGE is a separate command in Delta Lake.
- B. Correct.
Ensuring that the source files have deterministic filenames prevents duplicate file reads when using COPY INTO, which can help avoid duplicate records in the Delta table.
- C. Incorrect.
The 'OVERWRITE' option in COPY INTO replaces the entire target table's data, which is not suitable if only new records need to be added while avoiding duplicates.
- D. Incorrect.
The COPY INTO command does not support adding a 'WHERE NOT EXISTS' condition directly. Such logic must be implemented separately.
- E. Correct.
Delta tables can enforce uniqueness through constraints, such as primary keys or unique constraints, which can prevent duplicate records when used in conjunction with COPY INTO.