当插入触发器处于活动状态时，无法将 4 字节 UTF-8 字符/表情符号插入 MySQL 数据库

当查询包含 4 字节 UTF-8 字符时，我在使用记录对表执行的所有查询的数据库触发器时遇到问题。

My mysql.cnf https://pastebin.com/3cix3GzZ

Ubuntu 16.04 上的 mysql 版本为 5.7.19

示例脚本：

show variables where Variable_name like 'character\_set\_%' or Variable_name like 'collation%';

drop database if exists my_test_db;
create database my_test_db;
use my_test_db;

create table my_test_table(id int not null primary key auto_increment, jdoc json not null);
create table my_test_table_log(id int not null primary key auto_increment, query varchar(1024) NOT NULL);

SELECT "insert works when trigger is not active" as "";
insert into my_test_table(jdoc) VALUES(JSON_OBJECT("Dubai was", "????"));

DELIMITER |
CREATE TRIGGER log_my_test_table_queries_insert
BEFORE INSERT ON `my_test_table`
FOR EACH ROW
  BEGIN
    DECLARE original_query VARCHAR(1024);
    SET original_query = (SELECT info
                          FROM INFORMATION_SCHEMA.PROCESSLIST
                          WHERE id = CONNECTION_ID());
    INSERT INTO `my_test_table_log` (`query`) VALUES (original_query);
  END;
|
DELIMITER ;

SELECT "insert doesn't work when trigger is active" as "";
insert into my_test_table(jdoc) VALUES(JSON_OBJECT("Dubai was", "????"));

我的输出：

+--------------------------+--------------------+
| Variable_name            | Value              |
+--------------------------+--------------------+
| character_set_client     | utf8mb4            |
| character_set_connection | utf8mb4            |
| character_set_database   | utf8mb4            |
| character_set_filesystem | binary             |
| character_set_results    | utf8mb4            |
| character_set_server     | utf8mb4            |
| character_set_system     | utf8               |
| collation_connection     | utf8mb4_unicode_ci |
| collation_database       | utf8mb4_unicode_ci |
| collation_server         | utf8mb4_unicode_ci |
+--------------------------+--------------------+
10 rows in set (0.00 sec)

Query OK, 2 rows affected (0.03 sec)

Query OK, 1 row affected (0.00 sec)

Database changed
Query OK, 0 rows affected (0.03 sec)

Query OK, 0 rows affected (0.02 sec)

+-----------------------------------------+
|                                         |
+-----------------------------------------+
| insert works when trigger is not active |
+-----------------------------------------+
1 row in set (0.00 sec)

Query OK, 1 row affected (0.00 sec)

Query OK, 0 rows affected (0.01 sec)

+--------------------------------------------+
|                                            |
+--------------------------------------------+
| insert doesn't work when trigger is active |
+--------------------------------------------+
1 row in set (0.01 sec)

ERROR 1366 (HY000): Incorrect string value: '\xF0\x9F\x94\xA5")...' for column 'INFO' at row 1

数据库似乎是使用正确的字符集创建的

SHOW CREATE TRIGGER log_my_test_table_queries_insert;
SHOW CREATE TABLE my_test_table;
SHOW CREATE TABLE my_test_table_log;

outputs https://pastebin.com/yRP6RDSq

详细信息 详细信息 详细信息

发生这种情况是因为information_schema.processlist使用UTF8mb3字符集。 （UTF 是 UTFmb3 的别名）。这个简单的查询说明了这一点：

mysql> select info, "????" from information_schema.processlist;
+------------------------------------------------------+------+
| info                                                 | ?    |
+------------------------------------------------------+------+
| select info, "?" from information_schema.processlist | ????     |
+------------------------------------------------------+------+
1 row in set, 1 warning (0,00 sec)

Warning (Code 1366): Incorrect string value: '\xF0\x9F\x94\xA5" ...' for column 'INFO' at row 1

当触发器尝试插入内容时，上述警告可能会导致错误info列到另一个表中。

我认为问题在于查询字符串按原样存储在processlist表而不将其转换为预期的字符集。我已经提交了一份错误报告 http://bugs.mysql.com/bug.php?id=87579对这个。