ClickHouse/docs/en/sql-reference/statements/alter/apply-deleted-mask.md

slug	sidebar_position	sidebar_label
/en/sql-reference/statements/alter/apply-deleted-mask	46	APPLY DELETED MASK

Apply mask of deleted rows

ALTER TABLE [db].name [ON CLUSTER cluster] APPLY DELETED MASK [IN PARTITION partition_id]

The command applies mask created by lightweight delete and forcefully removes rows marked as deleted from disk. This command is a heavyweight mutation and it semantically equals to query ALTER TABLE [db].name DELETE WHERE _row_exists = 0.

:::note It only works for tables in the MergeTree family (including replicated tables). :::

See also

• Lightweight deletes
• Heavyweight deletes