[IMPALA-10836] Add simplify cast rule

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.1.0
• Component/s: Frontend
• Epic Color: ghx-label-4
• Assignee: Sheng Wang
• Reporter: Xianqing He
• Created: 03/Aug/21 03:43
• Updated: 14/Sep/22 09:27
• Resolved: 02/Nov/21 09:09

Description

For the function cast we can add the following optimizations:

1. Removes the inner case conversion expressions that are unnecessary, e.g. cast(cast(col as int) as string) => cast(col as string)
2. Removes unnecessary cast when the input is already the correct type, e.g. col is bigint, cast(col as bigint) => col

Issue Links

• causes: IMPALA-11049 Order by clause contains cast expr execute failed after 'SimplifyCastExprRule' rewrite
• is duplicated by: IMPALA-10969 Remove unnecessary cast in query