MySQL 8.0.26版本升級32版本查詢數據為空的跟蹤

某業務系統將MySQL 8.0.26升級為GreatSQL 8.0.32-24 後，某些特定的SQL語句不能查詢到數據。經測試 MySQL 8.0.32也存在相同的問題

此BUG已在 GreatSQL 8.0.32-25 版本中解決

MySQL 8.0.26版本升級32版本查詢數據為空的跟蹤

接到客戶反饋的問題後，對問題進行了復現和分析。

版本信息

greatsql> select version();
+-----------+
| version() |
+-----------+
| 8.0.32-24 |
+-----------+
1 row in set (0.00 sec)

建表語句

greatsql> show create table t_student;
CREATE TABLE `t_student1` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `age` int NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

表數據

greatsql> select * from t_student;
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  1 | abc    |  10 |
|  2 | 湯姆   |  20 |
+----+--------+-----+
2 rows in set (0.08 sec)

查詢數據

greatsql>  select * from (select * from t_student union select * from t_student) temp where name='湯姆';
Empty set, 2 warnings (0.00 sec)

greatsql> show warnings;
+---------+------+-------------------------------------------------------------------------+
| Level   | Code | Message                                                                 |
+---------+------+-------------------------------------------------------------------------+
| Warning | 1300 | Cannot convert string '\xE6\xB1\xA4\xE5\xA7\x86' from utf8mb4 to binary |
| Warning | 1300 | Cannot convert string '\xE6\xB1\xA4\xE5\xA7\x86' from utf8mb4 to binary |
+---------+------+-------------------------------------------------------------------------+
2 rows in set (0.00 sec)

greatsql> select * from (select * from t_student union select * from t_student) temp;
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  1 | abc    |  10 |
|  2 | 湯姆   |  20 |
+----+--------+-----+
2 rows in set (0.00 sec)

greatsql> select * from (select * from t_student union select * from t_student) temp where name='abc';
+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | abc  |  10 |
+----+------+-----+
1 row in set (0.00 sec)

可以看到 直接查詢temp這個view或者 在視圖上添加英文過濾條件均能查詢出數據，在view上添加中文過濾條件sql語句返回結果為空，有warnings提醒，warnings具體內容為Cannot convert string

在官方網站進行搜索，以下連接有相似內容：

https://bugs.mysql.com/bug.php?id=110228

https://bugs.mysql.com/bug.php?id=110955

MySQL 8.0.32版本中對於UNION/UNION ALL 後的結果中的字元串欄位過濾篩選不生效，客戶端中提示：

Cannot convert string '%\x...' from utf8mb4 to binary

官方已確認是8.0.32中的一個bug，已在8.0.33版本中修複，對於8.0.32版本，官方給出的解決方式如下：

set optimizer_switch="derived_condition_pushdown=off";

讓所有Session都生效，需要在配置文件中將optimizer_switch設置為off

此BUG已在 GreatSQL 8.0.32-25 版本中解決

解決方法

方法一：

設置set optimizer_switch="derived_condition_pushdown=off";後SQL語句能正常執行

greatsql> set optimizer_switch='derived_condition_pushdown=off';
Query OK, 0 rows affected (0.00 sec)

greatsql> select * from (select * from t_student union select * from t_student) temp where name='湯姆';
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  2 | 湯姆   |  20 |
+----+--------+-----+
1 row in set (0.00 sec)

方法二：

對單個SQL語句設置NO_DERIVED_CONDITION_PUSHDOWN hint

greatsql> set optimizer_switch='derived_condition_pushdown=on';
Query OK, 0 rows affected (0.00 sec)

greatsql> select * from (select * from t_student union select * from t_student) temp where name='湯姆';
Empty set, 2 warnings (0.00 sec)

greatsql> select  /*+ NO_DERIVED_CONDITION_PUSHDOWN(temp) */ * from (select * from t_student union select * from t_student) temp where name='湯姆';
+----+--------+-----+
| id | name   | age |
+----+--------+-----+
|  2 | 湯姆   |  20 |
+----+--------+-----+
1 row in set (0.00 sec)

Enjoy GreatSQL