[KYLIN-4620] sum(expression) support should be limited since it's not conform the associative law of addition in standard sql

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Zhong Yanghong
• Reporter: Zhong Yanghong
• Created: 03/Jul/20 10:19
• Updated: 08/Sep/20 11:48

Description

In standard sql, there's an edge case for the calculation of expression for a single row. For example, 

${col1} + ${col2}

if ${col1} or ${col2} is null, the result of this expression should be null. Therefore, the sum aggregation function does not conform the associative law of addition. That is

sum(col1) + sum(col2) != sum(col1 + col2) 

 

To support sum(col1 + col2), we have to predefine the it if null values may exist for the related columns.

If you want to enable sum(expression) with regarding null as 0, you need to set kylin.query.is-null-as-zero-in-expression to be true at project level

Issue Links

• relates to: KYLIN-3359 Support sum(expression) if possible