Fixed mdev-15162 Query with CTE hangs if assignment operator (:=) is used

If setting user variable was used in the specification of a recursive CTE
then Item_func_set_user_var::fix_fields() went into an infinite loop.

1 files changed, 12 insertions, 0 deletions

diff --git a/mysql-test/t/cte_recursive.test b/mysql-test/t/cte_recursive.test
index d2e33b165f7..5f1a7d4e1bf 100644
--- a/mysql-test/t/cte_recursive.test
+++ b/mysql-test/t/cte_recursive.test
@@ -2113,3 +2113,15 @@ DROP TABLE a_tbl;
 
 --error ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT
 WITH RECURSIVE x AS (SELECT 1,2 UNION ALL SELECT 1 FROM x) SELECT * FROM x;
+
+--echo #
+--echo # MDEV-15162: Setting user variable in recursive CTE
+--echo #
+
+SET @c=1;
+
+WITH RECURSIVE cte AS
+	(SELECT 5
+	UNION
+	SELECT @c:=@c+1 FROM cte WHERE @c<3)
+SELECT * FROM cte;