[CALCITE-1851] Decorrelation should get rid of correlated predicates while decorrelation filter condition

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: core
• Assignee: Unassigned
• Reporter: Vineet Garg
• Created: 20/Jun/17 00:49
• Updated: 22/Feb/19 01:21

Description

For queries such as

select sal from emp
where empno IN (
  select deptno from dept
  where emp.job = dept.name)

Filter condition for correlated predicate e.g. =($cor0.JOB, $1) is transformed into equality predicate on same column e.g. $1=$1 after calling decorrelateExpr (if value generator is not generated). This is further simplified into $1 is not null.
We do not need to generate and simplify such predicate expression, instead it could be completely removed. This will help support cases other than equality correlated predicates for which value generated is not required.