MDEV-16325 CREATE..SELECT..UNION creates a wrong field type for old varchar

- Adding Type_handler::traditional_merge_field_type()
- Removing real_type_to_type(), field_merge_type()
- Making Type_handler_var_string to merge as VARCHAR
- Additionally, fixing Field_string::print() to add the "/*old*/"
  comment into the data type for the old VARCHAR.
  This is similar to what MDEV-8267 earlier did for old DECIMAL.
- Adding tests

1 files changed, 0 insertions, 26 deletions

diff --git a/sql/field.h b/sql/field.h
index 5313f35d81a..eb4be46d3a0 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -467,31 +467,6 @@ inline bool is_temporal_type_with_date(enum_field_types type)
 }
 
 
-/**
-  Convert temporal real types as retuned by field->real_type()
-  to field type as returned by field->type().
-  
-  @param real_type  Real type.
-  @retval           Field type.
-*/
-inline enum_field_types real_type_to_type(enum_field_types real_type)
-{
-  switch (real_type)
-  {
-  case MYSQL_TYPE_TIME2:
-    return MYSQL_TYPE_TIME;
-  case MYSQL_TYPE_DATETIME2:
-    return MYSQL_TYPE_DATETIME;
-  case MYSQL_TYPE_TIMESTAMP2:
-    return MYSQL_TYPE_TIMESTAMP;
-  case MYSQL_TYPE_NEWDATE:
-    return MYSQL_TYPE_DATE;
-  /* Note: NEWDECIMAL is a type, not only a real_type */
-  default: return real_type;
-  }
-}
-
-
 enum enum_vcol_info_type
 {
   VCOL_GENERATED_VIRTUAL, VCOL_GENERATED_STORED,
@@ -873,7 +848,6 @@ public:
   {
     return type_handler()->cmp_type();
   }
-  static enum_field_types field_type_merge(enum_field_types, enum_field_types);
   virtual bool eq(Field *field)
   {
     return (ptr == field->ptr && null_ptr == field->null_ptr &&