ALTER TASK

Introduced or updated: v1.2.371

The ALTER TASK statement is used to modify an existing task.

NOTICE: this functionality works out of the box only in Databend Cloud.

Syntax

--- suspend or resume a task
ALTER TASK [ IF EXISTS ] <name> RESUME | SUSPEND

--- change task settings
ALTER TASK [ IF EXISTS ] <name> SET
  [ WAREHOUSE = <string> ]
  [ SCHEDULE = { <number> MINUTE | <number> SECOND | USING CRON <expr> <time_zone> } ]
  [ SUSPEND_TASK_AFTER_NUM_FAILURES = <num ]
  [ ERROR_INTEGRATION = <string> ]
   [ <session_parameter> = <value> [ , <session_parameter> = <value> ... ] ]
  [ COMMENT = <string> ]

--- change task SQL
ALTER TASK [ IF EXISTS ] <name> MODIFY AS <sql>

--- modify DAG when condition and after condition
ALTER TASK [ IF EXISTS ] <name> REMOVE AFTER <string> [ , <string> , ... ] | ADD AFTER <string> [ , <string> , ... ]
--- allow to change condition for task execution
ALTER TASK [ IF EXISTS ] <name> MODIFY WHEN <boolean_expr>

Parameter	Description
IF EXISTS	Optional. If specified, the task will only be altered if a task of the same name already exists.
name	The name of the task. This is a mandatory field.
RESUME | SUSPEND	Resume or suspend the task.
SET	Change task settings. details parameter descriptions could be found on see Create Task.
MODIFY AS	Change task SQL.
REMOVE AFTER	Remove predecessor tasks from the task dag, task would become a standalone task or a root task if no predecessor tasks left.
ADD AFTER	Add predecessor tasks to the task dag.
MODIFY WHEN	Change the condition for task execution.

Examples

ALTER TASK IF EXISTS mytask SUSPEND;

This command suspends the task named mytask if it exists.

ALTER TASK IF EXISTS mytask SET
  WAREHOUSE = 'new_warehouse'
  SCHEDULE = USING CRON '0 12 * * * *' 'UTC';

This example alters the mytask task, changing its warehouse to new_warehouse and updating its schedule to run daily at noon UTC.

ALTER TASK IF EXISTS mytask MODIFY 
AS
INSERT INTO new_table SELECT * FROM source_table;

Here, the SQL statement executed by mytask is changed to insert data from source_table into new_table.

ALTER TASK mytaskchild MODIFY WHEN STREAM_STATUS('stream3') = False;

In this example, we are modifying the mytaskchild task to change its WHEN condition. The task will now only run if the STREAM_STATUS function for 'stream3' evaluates to False. This means the task will execute when 'stream3' does not contain change data.

ALTER TASK MyTask1 ADD AFTER 'task2', 'task3';

In this example, we are adding dependencies to the MyTask1 task. It will now run after the successful completion of both 'task2' and 'task3'. This creates a dependency relationship in a Directed Acyclic Graph (DAG) of tasks.

ALTER TASK MyTask1 REMOVE AFTER 'task2';

Here, we are removing a specific dependency for the MyTask1 task. It will no longer run after 'task2'. This can be useful if you want to modify the task's dependencies within a DAG of tasks.