MDEV-15581 Incorrect result (missing row) with UNION DISTINCT in anchor parts

The current code does not support recursive CTEs whose specifications
contain a mix of ALL UNION and DISTINCT UNION operations.
This patch catches such specifications and reports errors for them.

1 files changed, 20 insertions, 0 deletions

diff --git a/mysql-test/r/cte_recursive.result b/mysql-test/r/cte_recursive.result
index b7516b88f9a..2e93e9f6ff8 100644
--- a/mysql-test/r/cte_recursive.result
+++ b/mysql-test/r/cte_recursive.result
@@ -3243,3 +3243,23 @@ SELECT 1 FROM qn
 ORDER BY (SELECT * FROM qn))
 SELECT count(*) FROM qn;
 ERROR 42000: This version of MariaDB doesn't yet support 'global ORDER_BY/LIMIT in recursive CTE spec'
+#
+# MDEV-15581: mix of ALL and DISTINCT UNION in recursive CTE
+#
+create table t1(a int);
+insert into t1 values(1),(2);
+insert into t1 values(1),(2);
+set @c=0, @d=0;
+WITH RECURSIVE qn AS
+(
+select 1,0 as col from t1
+union distinct
+select 1,0 from t1
+union all
+select 3, 0*(@c:=@c+1) from qn where @c<1
+union all
+select 3, 0*(@d:=@d+1) from qn where @d<1
+)
+select * from qn;
+ERROR 42000: This version of MariaDB doesn't yet support 'mix of ALL and DISTINCT UNION operations in recursive CTE spec'
+drop table t1;