Transformers are character set unaware

In transformers - where $return_type is being used without copying the original character set definition - there is a potential for data compare failures which are false positives.

Example: a table with a utf8 varchar column. The transformer uses $return_type and sees "varchar". It is however not aware of the utf8. Now the transformer may create a function, SP, table etc. and use this $return_type for variables within it, but it will not specify the original character set. Hence, differences between the original data and transformed data are likely/possible.

Note that for instance a varchar type (which normal maximum lenght is about 65K) in utf8 can at maximum be about 21-22K long, since utf8 uses 3 bytes:

mysql> CREATE TABLE t1 (txt1 VARCHAR(65000)) ENGINE=MyISAM;
Query OK, 0 rows affected (0.02 sec)

mysql> DROP TABLE t1;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE t1 (txt1 VARCHAR(65000) CHARACTER SET utf8) ENGINE=MyISAM;
Query OK, 0 rows affected, 1 warning (0.03 sec)

mysql> SHOW WARNINGS;
+-------+------+-----------------------------------------------+
| Level | Code | Message |
+-------+------+-----------------------------------------------+
| Note | 1246 | Converting column 'txt1' from VARCHAR to TEXT |
+-------+------+-----------------------------------------------+
1 row in set (0.00 sec)

mysql> DROP TABLE t1;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE t1 (txt1 VARCHAR(20000) CHARACTER SET utf8) ENGINE=MyISAM;
Query OK, 0 rows affected (0.03 sec)