MDEV-20496 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata

mysql-test/main/type_bit.result

@@ -878,3 +878,26 @@ DROP TABLE t1;
 #
 # End of 10.4 tests
 #
+#
+# Start of 10.5 tests
+#
+#
+# MDEV-20496 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata
+#
+CREATE TABLE t1 (b BIT(1));
+SELECT MIN(CASE WHEN 0 THEN b END) FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					MIN(CASE WHEN 0 THEN b END)	8	1	0	Y	32928	0	63
+MIN(CASE WHEN 0 THEN b END)
+NULL
+CREATE TABLE t2 AS SELECT MIN(CASE WHEN 0 THEN b END) FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `MIN(CASE WHEN 0 THEN b END)` bigint(1) unsigned DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t2;
+DROP TABLE t1;
+#
+# End of 10.5 tests
+#

mysql-test/main/type_bit.test

@@ -511,3 +511,26 @@ DROP TABLE t1;
 --echo #
 --echo # End of 10.4 tests
 --echo #
+
+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-20496 Assertion `field.is_sane()' failed in Protocol_text::store_field_metadata
+--echo #
+
+CREATE TABLE t1 (b BIT(1));
+--disable_ps_protocol
+--enable_metadata
+SELECT MIN(CASE WHEN 0 THEN b END) FROM t1;
+--disable_metadata
+--enable_ps_protocol
+CREATE TABLE t2 AS SELECT MIN(CASE WHEN 0 THEN b END) FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t2;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/sql_type.h

@@ -5391,6 +5391,7 @@ class Type_handler_bit: public Type_handler_int_result
   virtual ~Type_handler_bit() {}
   const Name name() const override { return m_name_bit; }
   enum_field_types field_type() const override { return MYSQL_TYPE_BIT; }
+  uint flags() const override { return UNSIGNED_FLAG; }
   protocol_send_type_t protocol_send_type() const override
   {
     return PROTOCOL_SEND_STRING;