(Questa non è davvero una risposta, ma un tentativo di isolare ciò che causa il problema e ciò che potrebbe risolverlo.)
Entra in un DATABASE con un CHARACTER SET del tutto irrilevante e COLLATION .
mysql> CREATE DATABASE `so40064402` /*!40100 DEFAULT CHARACTER SET ucs2 COLLATE ucs2_bin */
mysql> USE so40064402;
Database changed
Stabilisci utf8_polish per il cliente:
mysql> SET NAMES utf8 COLLATE utf8_polish_ci;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW VARIABLES LIKE 'c%a%t%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 | -- from SET NAMES
| character_set_connection | utf8 | -- from SET NAMES
| character_set_database | ucs2 | -- from DATABASE
| character_set_filesystem | binary | -- (constant)
| character_set_results | utf8 | -- from SET NAMES
| character_set_server | utf8mb4 |
| character_set_system | utf8 | -- (constant)
| character_sets_dir | /usr/share/mysql/charsets/ |
| collation_connection | utf8_polish_ci | -- from SET NAMES
| collation_database | ucs2_bin | -- from DATABASE
| collation_server | utf8mb4_unicode_520_ci |
+--------------------------+----------------------------+
11 rows in set (0.00 sec)
mysql> select charset(uuid()), collation(uuid());
+-----------------+-------------------+
| charset(uuid()) | collation(uuid()) |
+-----------------+-------------------+
| utf8 | utf8_general_ci | -- part of the problem, but can't fix this
+-----------------+-------------------+
1 row in set (0.00 sec)
mysql> select replace(uuid(),'-','');
ERROR 1270 (HY000): Illegal mix of collations
(utf8_general_ci,COERCIBLE),
(utf8_polish_ci,COERCIBLE),
(utf8_polish_ci,COERCIBLE) for operation 'replace'
mysql>
mysql>
mysql>
mysql> SET NAMES utf8mb4 COLLATE utf8mb4_polish_ci;
Query OK, 0 rows affected (0.00 sec)
Ora cambiamo SET NAMES solo. Ora funziona!?? Nonostante UUID() essendo utf8 !?
mysql> SHOW VARIABLES LIKE 'c%a%t%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8mb4 | -- from SET NAMES
| character_set_connection | utf8mb4 | -- from SET NAMES
| character_set_database | ucs2 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 | -- from SET NAMES
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
| collation_connection | utf8mb4_polish_ci | -- from SET NAMES
| collation_database | ucs2_bin |
| collation_server | utf8mb4_unicode_520_ci |
+--------------------------+----------------------------+
11 rows in set (0.00 sec)
mysql> select replace(uuid(),'-','');
+----------------------------------+
| replace(uuid(),'-','') |
+----------------------------------+
| ea841aacf83b11e8a66580fa5b3669ce |
+----------------------------------+
1 row in set (0.00 sec)
mysql>
