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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
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
《用三分钟学会一个MySQL知识》
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