Databricks Data Engineer Associate Question 352
Select 2A data engineer is using the COPY INTO statement to load data from a cloud storage location into a Delta table. However, they notice that no new records are being added to the target table, even though new files have been placed in the source directory. What could be the reason for this behavior?
- A
The Delta table's schema enforcement is rejecting the new records due to mismatched column names.
- B
The COPY INTO statement is skipping files that were already processed because they are tracked in the _delta_log.
- C
A WHERE clause in the COPY INTO statement is filtering out all the new data files.
- D
The source files have not been updated, and COPY INTO only processes files with a modification timestamp greater than the last load.
- E
The target Delta table is in read-only mode and cannot accept new data.
Show answer and explanation
Correct answers: B, C
Explanation
COPY INTO ensures that files are not duplicated in the target Delta table by using the _delta_log to track previously ingested files. If a file has already been processed, it will be skipped. Additionally, any filtering conditions specified in the WHERE clause of the COPY INTO statement could prevent new data from being ingested if they exclude the new files. These mechanisms ensure data integrity and avoid unnecessary duplication.
- A. Incorrect.
Schema enforcement issues would result in an error, not silent skipping of data. This option is incorrect.
- B. Correct.
COPY INTO uses the _delta_log to track already processed files and skips duplicates. If the files were already processed, they would not be re-ingested. This is a correct answer.
- C. Correct.
A WHERE clause in the COPY INTO statement could filter out files, preventing new data from being added to the table. This is a correct answer.
- D. Incorrect.
COPY INTO does not rely on file modification timestamps to skip files; it uses the _delta_log to track processed files. This option is incorrect.
- E. Incorrect.
Delta tables do not have a concept of a 'read-only mode' that prevents data from being added. This option is incorrect.