MySQL 错误？ "SHOW TABLE STATUS"报告导入期间行数波动

Question

我正在将 410 万条记录导入到离线系统中，以便对数据库的子集进行一些分析。当我运行导入时，我尝试使用以下方法检查其进度:

SHOW TABLE STATUS LIKE 'MailIssueElement'

奇怪的是......在不同的时间，我看到 Rows 的值较高和较低。我预计它只会上涨。以下是输出示例:

mysql> show table status like 'MailIssueElement' \G
*************************** 1. row ***************************
           Name: MailIssueElement
         Engine: MyISAM
        Version: 10
     Row_format: Dynamic
           Rows: 2818307
 Avg_row_length: 120
    Data_length: 338392232
Max_data_length: 281474976710655
   Index_length: 158029824
      Data_free: 0
 Auto_increment: 10248973
    Create_time: 2010-02-03 10:58:41
    Update_time: 2010-02-03 11:04:06
     Check_time: 2010-02-03 10:58:53
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.60 sec)

mysql> show table status like 'MailIssueElement' \G
*************************** 1. row ***************************
           Name: MailIssueElement
         Engine: MyISAM
        Version: 10
     Row_format: Dynamic
           Rows: 1870294
 Avg_row_length: 119
    Data_length: 223251912
Max_data_length: 281474976710655
   Index_length: 107688960
      Data_free: 0
 Auto_increment: 10248973
    Create_time: 2010-02-03 10:58:41
    Update_time: 2010-02-03 11:04:13
     Check_time: 2010-02-03 10:58:53
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.35 sec)

mysql> show table status like 'MailIssueElement' \G
*************************** 1. row ***************************
           Name: MailIssueElement
         Engine: MyISAM
        Version: 10
     Row_format: Dynamic
           Rows: 3074205
 Avg_row_length: 120
    Data_length: 369507112
Max_data_length: 281474976710655
   Index_length: 171537408
      Data_free: 0
 Auto_increment: 10248973
    Create_time: 2010-02-03 10:58:41
    Update_time: 2010-02-03 11:04:36
     Check_time: 2010-02-03 10:58:53
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.01 sec)

mysql> show table status like 'MailIssueElement' \G
*************************** 1. row ***************************
           Name: MailIssueElement
         Engine: MyISAM
        Version: 10
     Row_format: Dynamic
           Rows: 1870294
 Avg_row_length: 119
    Data_length: 223251912
Max_data_length: 281474976710655
   Index_length: 107688960
      Data_free: 0
 Auto_increment: 10248973
    Create_time: 2010-02-03 10:58:41
    Update_time: 2010-02-03 11:04:40
     Check_time: 2010-02-03 10:58:53
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.00 sec)

此行为有解释吗？有没有更好的方法来检查导入进度？

运行以下版本:服务器版本:5.0.32-Debian_7etch11-log Debian etch 发行版

---

编辑:

这是 DDL。这是一个MyISAM表:

mysql> show create table MailIssueElement \G
*************************** 1. row ***************************
       Table: MailIssueElement
Create Table: CREATE TABLE `MailIssueElement` (
  `Id` int(11) NOT NULL auto_increment,
  `IssueId` int(11) NOT NULL default '0',
  `Date` datetime NOT NULL default '0000-00-00 00:00:00',
  `Direction` enum('inbound','outbound') NOT NULL default 'inbound',
  `ToAddr` varchar(255) NOT NULL default '',
  `FromAddr` varchar(255) NOT NULL default '',
  `CCAddrs` varchar(255) NOT NULL default '',
  `Subject` text NOT NULL,
  `ParentIssueElementId` int(11) default NULL,
  `ParentIssueElementType` enum('mail','phone') default 'mail',
  `AgentId` int(11) NOT NULL default '0',
  PRIMARY KEY  (`Id`),
  KEY `date_idx` (`Date`),
  KEY `IssueId` (`IssueId`),
  KEY `idx_agent_id` (`AgentId`)
) ENGINE=MyISAM AUTO_INCREMENT=15099881 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

提前致谢，

-aj

Answer 1

关于行数

Some storage engines, such as MyISAM, store the exact count. For other storage engines, such as InnoDB, this value is an approximation, and may vary from the actual value by as much as 40 to 50%.

取自 MySQL :: MySQL 5.1 Reference Manual - SHOW TABLE STATUS Syntax