5.7 与 8.0 对相同文件的 LOAD DATA 语句结果不同

5.7 与 8.0 对相同文件的 LOAD DATA 语句结果不同

问题描述

某客户现场支持，由MySQL 5.7.21升级MySQL 8.0.25后，通过LOAD DATA导入文件，当同一会话连续导入不同的编码（UTF8/GB18030）文件时会出现乱码。数据库版本未升级之前，相同的导入操作在MySQL 5.7.21未出现乱码。

问题分析

1）查看简化后的 LOAD DATA语句

greatsql> LOAD DATA LOCAL INFILE '/home/greatdb/TEST_UTF8_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET UTF8MB4 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING UTF8MB4)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> LOAD DATA LOCAL INFILE '/home/greatdb/TEST_GB18030_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET GB18030 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING GB18030)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0

2）查看表数据

+----------+------------------------------------------------------+
| AUTO_INC | D_NAME                                               |
+----------+------------------------------------------------------+
|        1 | xxx社会保险xxx                                        |
|        2 | xxx市路桥区xxx                                        |
|        4 | 鍙板窞甯傝矾妗ュ尯绀句細淇濋櫓浜嬩笟绠＄悊涓績             |
|        5 | 鍙板窞甯傝矾妗ュ尯绀句細淇濋櫓浜嬩笟绠＄悊涓績             |
+----------+------------------------------------------------------+
4 rows in set (0.00 sec)

3）检查业务表的字符集与校验集，发现字符集为 utf8mb4 、校验集为 utf8mb4_bin

4）检查数据库的字符集与校验集

greatsql> SHOW GLOBAL VARIABLES LIKE '%char%';
+--------------------------------------+--------------------------------+
| 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                 | utf8mb3                        |
| character_sets_dir                   | /opt/mysql3301/share/charsets/ |
| validate_password_special_char_count | 1                              |
+--------------------------------------+--------------------------------+
9 rows in set (0.01 sec)
 
greatsql> SHOW GLOBAL VARIABLES LIKE '%coll%';
+-------------------------------+--------------------+
| Variable_name                 | Value              |
+-------------------------------+--------------------+
| collation_connection          | utf8mb4_bin        |
| collation_database            | utf8mb4_bin        |
| collation_server              | utf8mb4_bin        |
| default_collation_for_utf8mb4 | utf8mb4_general_ci |
+-------------------------------+--------------------+
4 rows in set (0.00 sec)

程序在MySQL 5.7.21跑了很长时间，一直没有问题，把数据库升级MySQL 8.0.25后，新导入的数据出现部分乱码， 由此怀疑，MySQL 8.0定长数据导入LOAD DATA @row 出现BUG。

BUG场景：同一个会话 LOAD DATA多种字符集文件，使用@临时变量切割字段。将导致导入数据乱码，向MySQL官方提BUG,已证实为BUG（编号115824）

问题复现

MySQL: 8.0.25

greatsql> SELECT VERSION();
+-----------+
| version() |
+-----------+
| 8.0.25    |
+-----------+
1 row in set (0.00 sec)
 
 
table ddl:
CREATE TABLE `assp_sis_payres_imp_bak` (
  `AUTO_INC` bigint unsigned NOT NULL AUTO_INCREMENT COMMENT '自增列',
  `D_NAME` varchar(210) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL,
  PRIMARY KEY (`AUTO_INC`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
 
 
greatsql> SHOW GLOBAL VARIABLES LIKE '%char%';
+--------------------------------------+--------------------------------+
| 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                 | utf8mb3                        |
| character_sets_dir                   | /opt/mysql3301/share/charsets/ |
| validate_password_special_char_count | 1                              |
+--------------------------------------+--------------------------------+
9 rows in set (0.01 sec)
 
greatsql> SHOW GLOBAL VARIABLES LIKE '%coll%';
+-------------------------------+--------------------+
| Variable_name                 | Value              |
+-------------------------------+--------------------+
| collation_connection          | utf8mb4_bin        |
| collation_database            | utf8mb4_bin        |
| collation_server              | utf8mb4_bin        |
| default_collation_for_utf8mb4 | utf8mb4_general_ci |
+-------------------------------+--------------------+
4 rows in set (0.00 sec)
 
greatsql> TRUNCATE TABLE assp_sis_payres_imp_bak;
Query OK, 0 rows affected (0.03 sec)
 
greatsql> SELECT charset(@row), @row;
+---------------+------------+
| charset(@row) | @row       |
+---------------+------------+
| binary        | NULL       |
+---------------+------------+
1 row in set (0.00 sec)
 
greatsql> LOAD DATA LOCAL INFILE '/root/dba_zc/load/TEST_UTF8_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET UTF8MB4 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING UTF8MB4)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SELECT charset(@row), @row;  
+---------------+------------------------+
| charset(@row) | @row                   |
+---------------+------------------------+
| utf8mb4       | XXX路桥区社会保XXX       |
+---------------+------------------------+
 
greatsql> LOAD DATA LOCAL INFILE '/root/dba_zc/load/TEST_GB18030_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET GB18030 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING GB18030)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SELECT charset(@row), @row;  
+---------------+-----------------------------------------+
| charset(@row) | @row                                    |
+---------------+-----------------------------------------+
| gb18030       | XXX路桥区社会保XXX       |
+---------------+-----------------------------------------+
 
greatsql>  SELECT * FROM  ASSP_SIS_PAYRES_IMP_BAK;
+----------+---------------------------------------------------------+
| AUTO_INC | D_NAME                                                  |
+----------+---------------------------------------------------------+
|        1 | XXX路桥区社会保XXX                                        |
|        2 | XXX路桥区社会保XXX                                        |
|        4 | 鍙板窞甯傝矾妗ュ尯绀句細淇濋櫓浜嬩笟绠＄悊涓績                 |
|        5 | 鍙板窞甯傝矾妗ュ尯绀句細淇濋櫓浜嬩笟绠＄悊涓績                 |
+----------+---------------------------------------------------------+
4 rows in set (0.00 sec)

MySQL 5.7.21

greatsql> SELECT VERSION();
+------------+
| version()  |
+------------+
| 5.7.21-log |
+------------+
1 row in set (0.01 sec)
 
table ddl:
CREATE TABLE `assp_sis_payres_imp_bak` (
  `AUTO_INC` bigint unsigned NOT NULL AUTO_INCREMENT COMMENT '自增列',
  `D_NAME` varchar(210) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL,
  PRIMARY KEY (`AUTO_INC`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
 
greatsql>  SHOW GLOBAL VARIABLES LIKE '%char%';
+--------------------------------------+--------------------------------+
| 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                           |
| character_sets_dir                   | /opt/mysql3305/share/charsets/ |
| validate_password_special_char_count | 1                              |
+--------------------------------------+--------------------------------+
9 rows in set (0.00 sec)
 
greatsql> SHOW GLOBAL VARIABLES LIKE '%coll%';
+----------------------+--------------------+
| Variable_name        | Value              |
+----------------------+--------------------+
| collation_connection | utf8mb4_general_ci |
| collation_database   | utf8mb4_general_ci |
| collation_server     | utf8mb4_general_ci |
+----------------------+--------------------+
3 rows in set (0.00 sec)
 
greatsql> SELECT charset(@row), @row;
+---------------+------------+
| charset(@row) | @row       |
+---------------+------------+
| binary        | NULL       |
+---------------+------------+
1 row in set (0.00 sec)
 
greatsql> LOAD DATA LOCAL INFILE '/root/dba_zc/load/TEST_UTF8_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET UTF8MB4 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING UTF8MB4)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SELECT charset(@row), @row;  
+---------------+-----------------------+
| charset(@row) | @row                  |
+---------------+-----------------------+
| utf8mb4       | XXX路桥区社会保XXX      |
+---------------+-----------------------+
 
greatsql> LOAD DATA LOCAL INFILE '/root/dba_zc/load/TEST_GB18030_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET GB18030 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING GB18030)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SELECT charset(@row), @row;  
+---------------+-----------------------+
| charset(@row) | @row                  |
+---------------+-----------------------+
| gb18030       | XXX路桥区社会保XXX      |
+---------------+-----------------------+
 
greatsql> SELECT * FROM  ASSP_SIS_PAYRES_IMP_BAK;                                                                                                                                                 
+---------------+-----------------------------+
| AUTO_INC      | D_NAME                      |
+---------------+-----------------------------+
|        1 | XXX路桥区社会保XXX                 |
|        2 | XXX路桥区社会保XXX                 |
|        4 | XXX路桥区社会保XXX                 |
|        5 | XXX路桥区社会保XXX                 |
+---------------+-----------------------------+
4 rows in set (0.00 sec)

BUG规避方案

通过SELECT``charset(@row), @row; 可以看到@row在执行LOAD DATA后在5.7.21和8.0.25是一样的，但最终的影响不一样。虽然MySQL官方确认此问题为BUG，但没有提供规避方案或者解决方案。通过万里工程师研究后，发现一种可行的规避方案。每次执行LOAD DATA命令前执行 [set @row=_binary'';] 进行规避。

greatsql> SELECT VERSION();
+-----------+
| version() |
+-----------+
| 8.0.25    |
+-----------+
1 row in set (0.00 sec)
 
greatsql> SET @row=_binary'';
Query OK, 0 rows affected (0.00 sec)
 
greatsql> LOAD DATA LOCAL INFILE '/home/greatdb/TEST_UTF8_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET UTF8MB4 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING UTF8MB4)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SET @row=_binary'';
Query OK, 0 rows affected (0.00 sec)
 
greatsql> LOAD DATA LOCAL INFILE '/home/greatdb/TEST_GB18030_bak.txt' IGNORE INTO TABLE ASSP_SIS_PAYRES_IMP_BAK CHARACTER SET GB18030 IGNORE 0 LINES  (@row) SET `D_NAME` = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row), 1,240)) USING GB18030)),'');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
 
greatsql> SELECT * FROM assp_sis_payres_imp_bak;
+----------+--------------------------------------------------+
| AUTO_INC | D_NAME                                           |
+----------+--------------------------------------------------+
|        1 | XXX路桥区社会保XXX                 |
|        2 | XXX路桥区社会保XXX                 |
|        4 | XXX路桥区社会保XXX                 |
|        5 | XXX路桥区社会保XXX                 |
+----------+--------------------------------------------------+
4 rows in set (0.00 sec)

问题总结

1.BUG原因

MySQL8.0重构定长数据导入LOAD DATA @row 出现BUG.同一个数据库会话，多次执行LOAD DATA @row命令，则第n次执行LOAD DATA @row 的字符集使用的是n-1次的字符集，当文件的字符集存在不同，例如先后处理GB18030、UTF8字符集的文件就会数据乱码。此问题MySQL官方已证实为BUG（编号115824）

2.BUG触发条件

触发条件：需同时满足以下三个条件才会触发此bug。

1）LOAD DATA命令使用类似 @row临时变量 进行数据处理，例如对定长记录按字节切割出多个字段：

LINES (@row) SET COLUMN_NAME = NULLIF(TRIM(CONVERT(UNHEX(SUBSTR(HEX(@row),1,20)) USING GB18030))。

2）在同一个连接中，多次执行LOAD DATA命令，且先后处理的文件字符集存在不同（例如GB18030和UTF8）。

3）使用MySQL 8.0。

3.BUG规避办法

由万里工程师提出，与MySQL官方社区沟通证实，涉及到满足上述BUG触发条件的场景，通过在每次执行LOAD DATA命令前执行 [set @row=_binary'';] 进行规避。

参考：https://bugs.mysql.com/bug.php?id=115824

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