​
ClickHouse function reference

​
aggThrow

Throws an exception with a specified probability. This function is primarily used for testing exception handling and safety in ClickHouse. Syntax: 
aggThrow(throw_prob)
Arguments:
  • throw_prob (Float64): The probability of throwing an exception. Value should be between 0 and 1.
Returns: This function doesn’t return a value. Instead, it throws an exception with the following message: 
Code: 503. DB::Exception: Aggregate function aggThrow has thrown exception successfully.
Example: 
SELECT
	taco_type,
	aggThrow(0.5) AS risky_taco_count
FROM
(
    SELECT 'Beef' AS taco_type
    UNION ALL
    SELECT 'Chicken' AS taco_type
    UNION ALL
    SELECT 'Vegetarian' AS taco_type
) AS taco_orders
GROUP BY
	taco_type;
This query attempts to count tacos by type, but has a 50% chance of throwing an exception for each group. If an exception is thrown, you might see: 
Received exception: Code: 503. DB::Exception: Aggregate function aggThrow has thrown exception successfully: While executing AggregatingTransform. (AGGREGATE_FUNCTION_THROW)
This function is not intended for use in production environments. It’s designed for testing how your system handles exceptions in aggregate functions.