DML操作报列不存在？_数组dml出错-优快云博客

DML操作报列不存在？

背景概述

客户在测试时发现执行某些DML语句时，出现了异常情况，报表不存在或者列不匹配的情况；

我在做数据迁移测试的时候也出现此问题，迁移数据时报 unknow column；

看到这种情况的时候很奇怪，查看表结构时也能看到当前执行的SQL语句涉及的表及列是存在的；

经过排查，最终发现当前这张表涉及触发器，报错的也不是这张表，而是其他表。

问题复现

本次测试基于 GreatSQL 8.0.32

1.创建测试表

greatsql> CREATE TABLE t1 (c1 int,c2 int,c3 int,c4 int);
greatsql> INSERT INTO t1 VALUES (1,1,1,1),(2,2,2,2),(3,3,3,3),(4,4,4,4);
greatsql> CREATE TABLE t2 (c5 int,c6 int,c7 int,c8 int);
greatsql> INSERT INTO t2 VALUES (1,1,1,1),(2,2,2,2),(3,3,3,3),(4,4,4,4);

2.创建触发器

# t2表不存在c1列
greatsql> CREATE TRIGGER test1
 after INSERT on t1
 FOR EACH ROW
 INSERT INTO t2(c1) values(NEW.c1);
Query OK, 0 rows affected (0.02 sec)

greatsql> CREATE TRIGGER test2
 after UPDATE on t1
 FOR EACH ROW
 UPDATE test.t2 SET c1=(NEW.c1)+1 WHERE c1=(NEW.c1);
Query OK, 0 rows affected (0.02 sec)

greatsql> CREATE TRIGGER test3
 after DELETE on t1
 FOR EACH ROW
 DELETE FROM t2 WHERE c1=(OLD.c1);
Query OK, 0 rows affected (0.02 sec)

# t3表不存在 
greatsql> CREATE TRIGGER test4
 before UPDATE on t2
 FOR EACH ROW
 INSERT INTO t3(c1) values(NEW.c5);
Query OK, 0 rows affected (0.00 sec)

可以看到在创建触发器的时候，不会去判断语句中涉及的表或者列是否存在。

3.执行测试SQL

greatsql> INSERT INTO test.t1 values (1,1,1,1);
ERROR 1054 (42S22): Unknown column 'c1' in 'field list'

greatsql> UPDATE test.t1 SET c1=110 WHERE c1=1;
ERROR 1054 (42S22): Unknown column 'c1' in 'field list'

greatsql> DELETE FROM  test.t1 WHERE c1=1;
ERROR 1054 (42S22): Unknown column 'c1' in 'where clause'

greatsql> UPDATE t2 SET c5=110 WHERE c5=1;
ERROR 1146 (42S02): Table 'test.t3' doesn't exist

此时报错c1列不存在，但没有显示是具体那张表的c1列，因此对我们产生误导，明明t1表存在c1列，但是还是报错c1列不存在；

4.故障排查

遇到上述问题时，我们可以打开通用日志，观察一下日志中记录的语句

shell> tail -f general5000.log
...
2024-10-14T16:21:16.837007+08:00         2651 Query     INSERT INTO test.t1 values (1,1,1,1)
2024-10-14T16:21:16.839500+08:00         2651 Query     INSERT INTO t2(c1) values(NEW.c1)
...

可以看到当我们执行了 INSERT INTO test.t1 语句后紧接着自动执行 INSERT INTO t2(c1) 语句，因为t2表没有c1列，所以报错 Unknown column 'c1'。

5.查看当前表涉及的触发器

greatsql> SELECT TRIGGER_SCHEMA,TRIGGER_NAME,EVENT_OBJECT_SCHEMA,EVENT_OBJECT_TABLE,ACTION_STATEMENT FROM INFORMATION_SCHEMA.TRIGGERS WHERE EVENT_OBJECT_TABLE='t1';
+----------------+--------------+---------------------+--------------------+----------------------------------------------------+
| TRIGGER_SCHEMA | TRIGGER_NAME | EVENT_OBJECT_SCHEMA | EVENT_OBJECT_TABLE | ACTION_STATEMENT                                   |
+----------------+--------------+---------------------+--------------------+----------------------------------------------------+
| test           | test1        | test                | t1                 | INSERT INTO t2(c1) values(NEW.c1)                  |
| test           | test2        | test                | t1                 | UPDATE test.t2 SET c1=(NEW.c1)+1 WHERE c1=(NEW.c1) |
| test           | test3        | test                | t1                 | DELETE FROM t2 WHERE c1=(OLD.c1)                   |
+----------------+--------------+---------------------+--------------------+----------------------------------------------------+
3 rows in set (0.00 sec)

当出现上面的问题时，可以查看一下这张表是否涉及触发器；如果涉及则检查一下对应触发器的ACTION_STATEMENT字段中的SQL语句涉及的表是否包含报错的字段。