[CALCITE-1016] "GROUP BY constant" on empty relation should return 0 rows

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.6.0
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 10/Dec/15 19:49
• Updated: 21/Jan/16 22:20
• Resolved: 14/Dec/15 01:18

Description

What should "GROUP BY 1" return on an empty table? Calcite currently returns 0 rows. Does that comply with the SQL standard?

Here is what Oracle 11.2.0.2.0 does.

SQL> select count(*) from emp where 1 = 0;

  COUNT(*)
----------
	 0

SQL> select count(*) from emp where 1 = 0 group by ();

no rows selected

SQL> select count(*) from emp where 1 = 0 group by 1;

no rows selected

SQL> select count(*) from emp;

  COUNT(*)
----------
	14

SQL> select count(*) from emp group by ();

  COUNT(*)
----------
	14

SQL> select count(*) from emp group by 1;

  COUNT(*)
----------
	14

I had expected

select count(*) from emp where 1 = 0 group by ()

would return 1 row, but it returns 0, like

group by 1

.

Issue Links

• is related to: HIVE-12640 Allow StatsOptimizer to optimize the query for Constant GroupBy keys