MDEV-20384 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata

mysql-test/main/type_year.result

@@ -587,3 +587,29 @@ DROP TABLE t1;
 #
 # End of 10.4 tests
 #
+#
+# Start of 10.5 tests
+#
+#
+# MDEV-20384 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata
+#
+CREATE TABLE t1 (a YEAR);
+INSERT INTO t1 VALUES (2000),(2001);
+SELECT MAX( NULLIF( a, 1970 ) ) AS f FROM t1;
+f
+2001
+SELECT NULLIF(a, 1970) AS f FROM t1 ORDER BY a;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					f	13	4	4	Y	32928	0	63
+f
+2000
+2001
+SELECT MAX(NULLIF(a, 1970)) AS f FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					f	8	4	4	Y	32928	0	63
+f
+2001
+DROP TABLE t1;
+#
+# End of 10.5 tests
+#

mysql-test/main/type_year.test

@@ -329,3 +329,27 @@ DROP TABLE t1;
 --echo #
 --echo # End of 10.4 tests
 --echo #
+
+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-20384 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata
+--echo #
+
+CREATE TABLE t1 (a YEAR);
+INSERT INTO t1 VALUES (2000),(2001);
+SELECT MAX( NULLIF( a, 1970 ) ) AS f FROM t1;
+--disable_ps_protocol
+--enable_metadata
+SELECT NULLIF(a, 1970) AS f FROM t1 ORDER BY a;
+SELECT MAX(NULLIF(a, 1970)) AS f FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t1;
+
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/sql_type.h

@@ -5335,6 +5335,7 @@ class Type_handler_year: public Type_handler_int_result
   virtual ~Type_handler_year() {}
   const Name name() const override { return m_name_year; }
   enum_field_types field_type() const override { return MYSQL_TYPE_YEAR; }
+  uint flags() const override { return UNSIGNED_FLAG; }
   protocol_send_type_t protocol_send_type() const override
   {
     return PROTOCOL_SEND_SHORT;