To clean up unreferenced files from a Delta table while maintaining ACID properties, which command should be executed?

The command that should be executed to clean up unreferenced files from a Delta table while maintaining ACID properties is VACUUM. This command is specifically designed for Delta Lake, allowing users to reclaim storage space and manage data efficiently by removing obsolete files that are no longer referenced by the Delta table.

When you use VACUUM, it operates in accordance with ACID principles by ensuring that any files still needed for active queries or transactions are preserved. It only deletes files that are older than a specified retention period, protecting recent data and ongoing workloads. Thus, this command effectively balances the need for storage optimization with the integrity and reliability of the database operations.

In contrast, other commands like OPTIMIZE can compact smaller files into larger ones but do not delete unreferenced files. DELETE is used to remove specific records from the table, not to clean up unreferenced files. DROP is intended to remove the entire table and its files from the database, which is not suitable for selectively cleaning up unused files while retaining the table itself.