Description:
The COERCIBILITY() function almost always returns a non-NULL value, even for
NULL arguments. For example, if there is no default database, the
DATABASE() function returns NULL, but the coercibility is SYSCONST:
mysql> select database();
+------------+
| database() |
+------------+
| NULL |
+------------+
1 row in set (0.00 sec)
mysql> select coercibility(database());
+--------------------------+
| coercibility(database()) |
+--------------------------+
| 3 |
+--------------------------+
1 row in set (0.00 sec)
However, the character set and collation are NULL:
mysql> select charset(database());
+---------------------+
| charset(database()) |
+---------------------+
| NULL |
+---------------------+
1 row in set (0.00 sec)
mysql> select collation(database());
+-----------------------+
| collation(database()) |
+-----------------------+
| NULL |
+-----------------------+
1 row in set (0.00 sec)
Presumably the character set should be utf8, and the collation
should be utf_general_ci?
CHARSET() and COLLATION() also return NULL in other contexts:
- For column values that are NULL (should be column charset/collation)
- For user variables that are NULL (should be ???)
COERCIBILITY() does return NULL in one instance:
mysql> select coercibility(NULL);
+--------------------+
| coercibility(NULL) |
+--------------------+
| NULL |
+--------------------+
1 row in set (0.00 sec)
This should be fixed to return IGNORABLE.
How to repeat:
See above.
