[CALCITE-545] When a projected expression can only have one value, replace with that constant

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0.0-incubating
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 19/Dec/14 18:31
• Updated: 08/Feb/15 08:56
• Resolved: 27/Dec/14 05:41

Description

When we have deduced that an expression can only have one value, replace the expression with that value. This is beneficial because it will allow us to do more column trimming.

Example 1

select deptno from emp where deptno = 10

can become

select 10 from emp where deptno = 10

Example 2 (using inference, as in CALCITE-360)

select emp.deptno
from emp join dept using (deptno)
where dept.deptno = 10

can become

select 10
from emp join dept using (deptno)
where dept.deptno = 10