v.21.4New Features

Added SQL Command to Unfreeze Partitions in ClickHouse

Official CH changelog text
Added new SQL command ALTER TABLE 'table_name' UNFREEZE [PARTITION 'part_expr'] WITH NAME 'backup_name'. This command is needed to properly remove 'freezed' partitions from all disks. #21142 (Pavel Kovalenko).
Introduced the new SQL command ALTER TABLE 'table_name' UNFREEZE [PARTITION 'part_expr'] WITH NAME 'backup_name' to manage and remove frozen partitions.

Why it matters

This feature solves the problem of properly removing frozen partitions from all disks. Frozen partitions are snapshots stored on disk that need to be cleaned up reliably and completely to free up space and maintain storage hygiene.

How to use it

Use the ALTER TABLE statement with the UNFREEZE keyword to remove frozen partitions. Optionally specify a PARTITION 'part_expr' to target a specific partition, and use WITH NAME 'backup_name' to identify the frozen data to be unfrozen and deleted. Example:

ALTER TABLE 'table_name' UNFREEZE PARTITION '202301' WITH NAME 'backup_202301'

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