MDEV-8862 Wrong field type for MAX(COALESCE(datetime_column))

Author: Alexander Barkov

mysql-test/r/type_time.result

@@ -1206,5 +1206,14 @@ Warning	1292	Incorrect time value: '9000000' for column 'b' at row 4
 Warning	1292	Incorrect time value: '9000000' for column 'c' at row 4
 DROP TABLE t1;
 #
+# MDEV-8862 Wrong field type for MAX(COALESCE(datetime_column))
+#
+CREATE TABLE t1 (a TIME);
+INSERT INTO t1 VALUES ('10:10:10'),('10:20:30');
+SELECT MAX(a), MAX(COALESCE(a)) FROM t1;
+MAX(a)	MAX(COALESCE(a))
+10:20:30	10:20:30
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/type_time.test

@@ -715,6 +715,14 @@ INSERT INTO t1 VALUES (9000000,9000000,9000000);
 SELECT a, TIME(a),TIME(b),TIME(c) FROM t1 ORDER BY a;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-8862 Wrong field type for MAX(COALESCE(datetime_column))
+--echo #
+CREATE TABLE t1 (a TIME);
+INSERT INTO t1 VALUES ('10:10:10'),('10:20:30');
+SELECT MAX(a), MAX(COALESCE(a)) FROM t1;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item_func.cc

@@ -1089,7 +1089,9 @@ bool Item_func_hybrid_result_type::get_date(MYSQL_TIME *ltime,
  case STRING_RESULT:
  {
  if (is_temporal_type(field_type()))
- return date_op(ltime, fuzzydate);
+ return date_op(ltime,
+ fuzzydate |
+ (field_type() == MYSQL_TYPE_TIME ? TIME_TIME_ONLY : 0));
  char buff[40];
  String tmp(buff,sizeof(buff), &my_charset_bin),*res;
  if (!(res= str_op(&tmp)) ||