MDEV-11868: min ( distinct ) over ( ) returns wrong value

The bug was not visible in current HEAD. Introduced test case to catch
regressions. Also improve error messages regarding distinct usage in
window functions.

mysql-test/r/win.result

@@ -2958,3 +2958,94 @@ develop	2	4000	4000.0000
 sales	3	6000	5500.0000
 sales	4	5000	5500.0000
 drop table empsalary;
+#
+# MDEV-11868: min(distinct) over () returns wrong value
+#
+create table TDEC (CDEC int, RNUM int);
+create view VDEC as select * from TDEC;
+insert into TDEC (CDEC) values (null),(-1),(0),(1),(0),(10);
+select TDEC.CDEC, min(TDEC.CDEC) over () from TDEC;
+CDEC	min(TDEC.CDEC) over ()
+NULL	-1
+-1	-1
+0	-1
+1	-1
+0	-1
+10	-1
+select VDEC.CDEC, min(VDEC.CDEC) over () from VDEC;
+CDEC	min(VDEC.CDEC) over ()
+NULL	-1
+-1	-1
+0	-1
+1	-1
+0	-1
+10	-1
+select TDEC.CDEC, max(TDEC.CDEC) over () from TDEC;
+CDEC	max(TDEC.CDEC) over ()
+NULL	10
+-1	10
+0	10
+1	10
+0	10
+10	10
+select VDEC.CDEC, max(VDEC.CDEC) over () from VDEC;
+CDEC	max(VDEC.CDEC) over ()
+NULL	10
+-1	10
+0	10
+1	10
+0	10
+10	10
+select TDEC.CDEC, min(distinct TDEC.CDEC) over () from TDEC;
+CDEC	min(distinct TDEC.CDEC) over ()
+NULL	-1
+-1	-1
+0	-1
+1	-1
+0	-1
+10	-1
+select VDEC.CDEC, min(distinct VDEC.CDEC) over () from VDEC;
+CDEC	min(distinct VDEC.CDEC) over ()
+NULL	-1
+-1	-1
+0	-1
+1	-1
+0	-1
+10	-1
+select TDEC.CDEC, max(distinct TDEC.CDEC) over () from TDEC;
+CDEC	max(distinct TDEC.CDEC) over ()
+NULL	10
+-1	10
+0	10
+1	10
+0	10
+10	10
+select VDEC.CDEC, max(distinct VDEC.CDEC) over () from VDEC;
+CDEC	max(distinct VDEC.CDEC) over ()
+NULL	10
+-1	10
+0	10
+1	10
+0	10
+10	10
+#
+# These should be removed once support for them is added.
+#
+select TDEC.CDEC, count(distinct TDEC.CDEC) over () from TDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'COUNT(DISTINCT) aggregate as window function'
+select VDEC.CDEC, count(distinct VDEC.CDEC) over () from VDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'COUNT(DISTINCT) aggregate as window function'
+select TDEC.CDEC, sum(distinct TDEC.CDEC) over () from TDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'SUM(DISTINCT) aggregate as window function'
+select VDEC.CDEC, sum(distinct VDEC.CDEC) over () from VDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'SUM(DISTINCT) aggregate as window function'
+select TDEC.CDEC, avg(distinct TDEC.CDEC) over () from TDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'AVG(DISTINCT) aggregate as window function'
+select VDEC.CDEC, avg(distinct VDEC.CDEC) over () from VDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'AVG(DISTINCT) aggregate as window function'
+select TDEC.CDEC, GROUP_CONCAT(TDEC.CDEC) over () from TDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'GROUP_CONCAT() aggregate as window function'
+select VDEC.CDEC, GROUP_CONCAT(distinct VDEC.CDEC) over () from VDEC;
+ERROR 42000: This version of MariaDB doesn't yet support 'GROUP_CONCAT() aggregate as window function'
+drop table TDEC;
+drop view VDEC;

mysql-test/t/win.test

@@ -1734,3 +1734,43 @@ SELECT depname, empno, salary, avg(salary) OVER (PARTITION BY depname) FROM emps
 SELECT depname, empno, salary, avg(salary) OVER (PARTITION BY depname) FROM empsalary HAVING empno > 1 ORDER BY depname;
 
 drop table empsalary;
+
+--echo #
+--echo # MDEV-11868: min(distinct) over () returns wrong value
+--echo #
+
+create table TDEC (CDEC int, RNUM int);
+create view VDEC as select * from TDEC;
+insert into TDEC (CDEC) values (null),(-1),(0),(1),(0),(10);
+select TDEC.CDEC, min(TDEC.CDEC) over () from TDEC;
+select VDEC.CDEC, min(VDEC.CDEC) over () from VDEC;
+select TDEC.CDEC, max(TDEC.CDEC) over () from TDEC;
+select VDEC.CDEC, max(VDEC.CDEC) over () from VDEC;
+
+select TDEC.CDEC, min(distinct TDEC.CDEC) over () from TDEC;
+select VDEC.CDEC, min(distinct VDEC.CDEC) over () from VDEC;
+select TDEC.CDEC, max(distinct TDEC.CDEC) over () from TDEC;
+select VDEC.CDEC, max(distinct VDEC.CDEC) over () from VDEC;
+
+--echo #
+--echo # These should be removed once support for them is added.
+--echo #
+--error ER_NOT_SUPPORTED_YET
+select TDEC.CDEC, count(distinct TDEC.CDEC) over () from TDEC;
+--error ER_NOT_SUPPORTED_YET
+select VDEC.CDEC, count(distinct VDEC.CDEC) over () from VDEC;
+--error ER_NOT_SUPPORTED_YET
+select TDEC.CDEC, sum(distinct TDEC.CDEC) over () from TDEC;
+--error ER_NOT_SUPPORTED_YET
+select VDEC.CDEC, sum(distinct VDEC.CDEC) over () from VDEC;
+--error ER_NOT_SUPPORTED_YET
+select TDEC.CDEC, avg(distinct TDEC.CDEC) over () from TDEC;
+--error ER_NOT_SUPPORTED_YET
+select VDEC.CDEC, avg(distinct VDEC.CDEC) over () from VDEC;
+--error ER_NOT_SUPPORTED_YET
+select TDEC.CDEC, GROUP_CONCAT(TDEC.CDEC) over () from TDEC;
+--error ER_NOT_SUPPORTED_YET
+select VDEC.CDEC, GROUP_CONCAT(distinct VDEC.CDEC) over () from VDEC;
+
+drop table TDEC;
+drop view VDEC;

sql/sql_window.cc

@@ -2699,10 +2699,20 @@ bool Window_func_runner::add_function_to_run(Item_window_func *win_func)
   {
     /* Distinct is not yet supported. */
     case Item_sum::GROUP_CONCAT_FUNC:
+      my_error(ER_NOT_SUPPORTED_YET, MYF(0),
+               "GROUP_CONCAT() aggregate as window function");
+      return true;
     case Item_sum::SUM_DISTINCT_FUNC:
+      my_error(ER_NOT_SUPPORTED_YET, MYF(0),
+               "SUM(DISTINCT) aggregate as window function");
+      return true;
     case Item_sum::AVG_DISTINCT_FUNC:
       my_error(ER_NOT_SUPPORTED_YET, MYF(0),
-               "This aggregate as window function");
+               "AVG(DISTINCT) aggregate as window function");
+      return true;
+    case Item_sum::COUNT_DISTINCT_FUNC:
+      my_error(ER_NOT_SUPPORTED_YET, MYF(0),
+               "COUNT(DISTINCT) aggregate as window function");
       return true;
     default:
       break;