[CALCITE-4021] EnumerableUnion should preserve ordering when all inputs have the same collation

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Fix Version/s: 1.27.0
• Assignee: Rui Wang
• Reporter: Rui Wang
• Created: 23/May/20 17:30
• Updated: 13/Jan/23 00:53
• Resolved: 13/Jan/23 00:52

Description

For query:

select name from sales_dept
union 
select name from it_dept
order by mgr

We could generate a plan based on https://issues.apache.org/jira/browse/CALCITE-4017:

EnumerableUnion
    EnumerableProject
        EnumerableSort
           EnumerableTableScan[name="sales_dept"]
    EnumerableProject
        EnumerableSort
           EnumerableTableScan[name="it_dept"]

So EnumerableUnion should preserve ordering when all input have the same collation to make sure result of query is correct.

Issue Links

• relates to: CALCITE-3221 Add MergeUnion operator in Enumerable convention