VACUUM

Applies to: Databricks SQL Databricks Runtime

Remove unused files from a table directory.

Note

This command works differently depending on whether you’re working on a Delta or Apache Spark table.

Vacuum a Delta table

Recursively vacuum directories associated with the Delta table. For full details and limitations, see Remove unused data files with vacuum.

VACUUM removes all files from the table directory that are not managed by Delta, as well as data files that are no longer in the latest state of the transaction log for the table and are older than a retention threshold. VACUUM will skip all directories that begin with an underscore (_), which includes the _delta_log. Partitioning your table on a column that begins with an underscore is an exception to this rule; VACUUM scans all valid partitions included in the target Delta table. Delta table data files are deleted according to the time they have been logically removed from Delta’s transaction log plus retention hours, not their modification timestamps on the storage system. The default threshold is 7 days.

On Delta tables, Azure Databricks does not automatically trigger VACUUM operations.

If you run VACUUM on a Delta table, you lose the ability to time travel back to a version older than the specified data retention period.

Warning

It is recommended that you set a retention interval to be at least 7 days, because old snapshots and uncommitted files can still be in use by concurrent readers or writers to the table. If VACUUM cleans up active files, concurrent readers can fail or, worse, tables can be corrupted when VACUUM deletes files that have not yet been committed. You must choose an interval that is longer than the longest running concurrent transaction and the longest period that any stream can lag behind the most recent update to the table.

Delta Lake has a safety check to prevent you from running a dangerous VACUUM command. In Databricks Runtime, you are certain that there are no operations being performed on this table that take longer than the retention interval you plan to specify, you can turn off this safety check by setting the Spark configuration property spark.databricks.delta.retentionDurationCheck.enabled to false.

VACUUM table_name [RETAIN num HOURS] [DRY RUN]

Important

The retention window for the VACUUM command is determined by the delta.deletedFileRetentionDuration table property, which defaults to 7 days. This means VACUUM removes data files that are no longer referenced by a Delta table version in the last 7 days. If you’d like to retain data for longer (such as to support time travel for longer durations), you must set this table property to a higher value. The following example shows setting this threshold to 30 days:

ALTER TABLE table_name SET TBLPROPERTIES ('delta.deletedFileRetentionDuration' = '30 days');

Parameters

• table_name

  Identifies an existing Delta table. The name must not include a temporal specification.

• RETAIN num HOURS

  The retention threshold.

• DRY RUN

  Return a list of up to 1000 files to be deleted.

Vacuum a non-Delta table

Recursively vacuums directories associated with the non-Delta table and remove uncommitted files older than a retention threshold. The default threshold is 7 days.

On non-Delta tables, Azure Databricks automatically triggers VACUUM operations as data is written.

Syntax

VACUUM table_name [RETAIN num HOURS]

Parameters

• table_name

  Identifies an existing table by name or path.

• RETAIN num HOURS

  The retention threshold.