[CALCITE-895] Simplify "(CASE ... END) = constant" inside AND or OR

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.5.0
• Component/s: core
• Assignee: Julian Hyde
• Reporter: Sean Hsuan-Yi Chu
• Created: 21/Sep/15 22:38
• Updated: 27/Feb/24 22:24
• Resolved: 28/Sep/15 20:31

Description

ReduceExpressionsRule.FILTER_INSTANCE does not simplify a Filter, which has “Case-When IsNull” under OR or AND.

For example, a query like this:

select *
from emp
where case when sal = 1000 then null else 1 end is null OR sal = 2000

The condition in the filter can be rewritten as "sal = 1000 OR sal = 2000". However, for now, Calcite does not do the simplification. Instead, Calcite output this plan:

LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
  LogicalFilter(condition=[OR(IS NULL(CASE(=($5, 1000), null, 1)), =($5, 2000))])
    LogicalTableScan(table=[[CATALOG, SALES, EMP]])