Question

A data engineer inspects a Delta table's storage location in cloud object storage and finds a subfolder named _delta_log containing several JSON files and one Parquet checkpoint file, alongside the data Parquet files. A junior colleague asks what the _delta_log directory is responsible for. Which statement best describes its purpose?

Accepted Answer

It stores the ordered transaction log that records every commit, enabling ACID guarantees and time travel.

Answer

It caches query results so that repeated reads of the table return faster without scanning data files.

Answer

It holds backup copies of the data Parquet files in case the primary files become corrupted.

Answer

It contains the compiled physical execution plan generated by the Spark optimizer for the table.