[IMPALA-10969] Remove unnecessary cast in query

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: Impala 4.0.0
• Component/s: Frontend
• Epic Color: ghx-label-2
• Assignee: Unassigned
• Reporter: Sheng Wang
• Created: 14/Oct/21 02:31
• Updated: 14/Oct/21 06:28
• Resolved: 14/Oct/21 06:28

Description

In some queries, cast target data type is same as column origin data type. We can remove these unnecessary cast by adding a new expr rewrite rule. There are two benefits:

1. For non partition columns, remove these unnecessary cast will improve query performance;
2. If we visit kudu table, predicates with cast cannot push down to Kudu side, such as 'cast(a as int) > 100', but ' a > 100' can push down to kudu side. We can remove this cast if a is INT type.

Issue Links

• duplicates: IMPALA-10836 Add simplify cast rule