技术分享 | MySQL 在批量插入时捕捉错误信息

作者：杨涛涛

背景

今天的文章来源于今天客户问的一个问题。

问题大概意思是：我正在从 Oracle 迁移到 MySQL，数据已经转换为单纯的 INSERT 语句。由于语句很多，每次导入的时候不知道怎么定位到错误的语句。 如果 INSERT 语句少也就罢了，我可以手工看，不过 INSERT 语句很多，我怎么定位到是哪些语句出错了，我好改正呢？总不能每次遇到的错误的时候改一下，在重新运行继续改正吧？有没有简单点的方法。

其实 MySQL 自身就有错误诊断区域，如果能好好利用，则事半功倍。下面我来简单说下怎么使用错误诊断区域。

比如说我要插入的表结构为 n3, 保存错误信息的日志表为 error_log 两个表结构如下：

mysql
-- tables definition.
[ytt]>create table n3 (id int not null, id2 int generated always as ((mod(id,10))));
Query OK, 0 rows affected (0.04 sec)

[ytt]>create table error_log (sqltext text, error_no int unsigned, error_message text);
Query OK, 0 rows affected (0.04 sec)

假设插入的语句，为了演示，我这里仅仅简单写了 8 条语句。

mysql
-- statements body.
set @a1 = "INSERT INTO n3 (id) VALUES(100)";
set @a2 = "INSERT INTO n3 (id) VALUES('test')";
set @a3 = "INSERT INTO n3 (id) VALUES('test123')";
set @a4 = "INSERT INTO n3 (id) VALUES('123test')";
set @a5 = "INSERT INTO n3 (id) VALUES(200)";
set @a6 = "INSERT INTO n3 (id) VALUES(500)";
set @a7 = "INSERT INTO n3 (id) VALUES(null)";
set @a8 = "INSERT INTO n3 (id) VALUES(10000000000000)";

MySQL 的错误代码很多，不过总体归为三类：

• sqlwarning SQLSTATE 代码开始为 '01'
• not found SQLSTATE 代码开始为 '02'
• sqlexception SQLSTATE 代码开始非 '00','01','02' 的所有错误代码。

为了简单方便，我们写这些代码到存储过程里。以下为示例存储过程。

mysql
-- stored routines body.
drop procedure if exists sp_insert_simple;
delimiter ||
create procedure sp_insert_simple()
l1:begin
  DECLARE i,j TINYINT DEFAULT 1;   -- loop counter.
  DECLARE v_errcount,v_errno INT DEFAULT 0; -- error count and error number.
  DECLARE v_msg TEXT; -- error details.
  declare v_sql json; -- store statements list.
  declare v_sql_keys varchar(100); -- array index.
  declare v_sql_length int unsigned; -- array length.

  -- Handler declare.
  DECLARE CONTINUE HANDLER FOR SQLEXCEPTION,SQLWARNING,NOT FOUND  -- exception in mysql routines.
  l2:BEGIN
    get stacked diagnostics v_errcount = number;
    set j = 1;
    WHILE j <= v_errcount
    do
      GET stacked DIAGNOSTICS CONDITION j  v_errno = MYSQL_ERRNO, v_msg = MESSAGE_TEXT;
      -- record error messages into table.
      INSERT INTO error_log(sqltext,error_no,error_message) VALUES (@sqltext, v_errno,v_msg);
      SET j = j + 1;
    END WHILE;
  end;
  -- sample statements array.
  set v_sql = '{
        "a1": "INSERT INTO n3 (id) VALUES(100)",
        "a2": "INSERT INTO n3 (id) VALUES(''test'')",
        "a3": "INSERT INTO n3 (id) VALUES(''test123'')",
        "a4": "INSERT INTO n3 (id) VALUES(''123test'')",
        "a5": "INSERT INTO n3 (id) VALUES(200)",
        "a6": "INSERT INTO n3 (id) VALUES(500)",
        "a7": "INSERT INTO n3 (id) VALUES(null)",
        "a8": "INSERT INTO n3 (id) VALUES(10000000000000)"
}';
  set i = 1;
  set v_sql_length = json_length(v_sql);
  while i <=v_sql_length  do
    set v_sql_keys = concat('$.a',i);
    set @sqltext = replace(json_extract(v_sql,v_sql_keys),'"','');
    prepare s1 from @sqltext;
    execute s1;
    set i = i + 1;
  end while;
  drop prepare s1;
  -- invoke procedure.
  -- call sp_insert_simple;
end;
||
delimiter ;

我们来调用这个存储过程看下结果。

mysql
[(none)]>use ytt
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A    
Database changed

[ytt]>call sp_insert_simple;
Query OK, 0 rows affected (0.05 sec)

表N3的结果。

mysql
[ytt]>select  * from n3;
+-----+------+
| id  | id2  |
+-----+------+
| 100 |    0 |
| 200 |    0 |
| 500 |    0 |
+-----+------+
3 rows in set (0.00 sec)

错误日志记录了所有错误的语句。

mysql
[ytt]>select * from error_log;
+--------------------------------------------+----------+-------------------------------------------------------------+
| sqltext                                    | error_no | error_message                                               |
+--------------------------------------------+----------+-------------------------------------------------------------+
| INSERT INTO n3 (id) VALUES('test')         |     1366 | Incorrect integer value: 'test' for column 'id' at row 1    |
| INSERT INTO n3 (id) VALUES('test123')      |     1366 | Incorrect integer value: 'test123' for column 'id' at row 1 |
| INSERT INTO n3 (id) VALUES('123test')      |     1265 | Data truncated for column 'id' at row 1                     |
| INSERT INTO n3 (id) VALUES(null)           |     1048 | Column 'id' cannot be null                                  |
| INSERT INTO n3 (id) VALUES(10000000000000) |     1264 | Out of range value for column 'id' at row 1                 |
+--------------------------------------------+----------+-------------------------------------------------------------+
5 rows in set (0.00 sec)

其实这个问题如果用 Python 或 PHP 等外部语言来说，将会更简单，思路差不多。