Mysql – Maintain table with too many insert

I tried something similar just now

Here is MySQL for My PC

mysql> select * from information_schema.global_variables where variable_name='datadir' or variable_name like 'versio%';
+-------------------------+------------------------------+
| VARIABLE_NAME           | VARIABLE_VALUE               |
+-------------------------+------------------------------+
| VERSION_COMMENT         | MySQL Community Server (GPL) |
| VERSION                 | 5.5.12-log                   |
| VERSION_COMPILE_MACHINE | x86                          |
| DATADIR                 | C:\MySQL_5.5.12\data\        |
| VERSION_COMPILE_OS      | Win64                        |
+-------------------------+------------------------------+
5 rows in set (0.00 sec)

I will run this using MyISAM

• Step 01) create a table called 'rolando'
• Step 02) insert 'dominique' and 'diamond'
• Step 03) copy the table structure to 'pamela'
• Step 04) alter 'pamela' to not have auto_increment
• Step 05) In DOS, copy rolando.MYD to pamela.MYD
• Step 06) run REPAIR TABLE pamela; (Rebuild pamela.MYI)
• Step 07) run SELECT COUNT(1) FROM pamela;
• Step 08) run SHOW CREATE TABLE pamela\G
• Step 09) run SELECT * FROM pamela;
• Step 10) insert 'carlik' into pamela
• Step 11) run SELECT * FROM pamela;

Let's see if these steps are kosher.

Here are Steps 1-4

mysql> drop table if exists rolando;
Query OK, 0 rows affected (0.02 sec)

mysql> drop table if exists pamela;
Query OK, 0 rows affected (0.00 sec)

mysql> create table rolando
    -> (
    ->     name varchar(20),
    ->     id int not null auto_increment,
    ->     primary key (id)
    -> ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.05 sec)

mysql> insert into rolando (name) values ('dominique'),('diamond');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from rolando;
+-----------+----+
| name      | id |
+-----------+----+
| dominique |  1 |
| diamond   |  2 |
+-----------+----+
2 rows in set (0.00 sec)

mysql> create table pamela like rolando;
Query OK, 0 rows affected (0.05 sec)

mysql> show create table rolando\G
*************************** 1. row ***************************
       Table: rolando
Create Table: CREATE TABLE `rolando` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> show create table pamela\G
*************************** 1. row ***************************
       Table: pamela
Create Table: CREATE TABLE `pamela` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.02 sec)

mysql> alter table pamela modify id int(11) unsigned not null;
Query OK, 0 rows affected (0.11 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table pamela\G
*************************** 1. row ***************************
       Table: pamela
Create Table: CREATE TABLE `pamela` (
  `name` varchar(20) DEFAULT NULL,
  `id` int(11) unsigned NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> select count(1) from pamela;
+----------+
| count(1) |
+----------+
|        0 |
+----------+
1 row in set (0.01 sec)

mysql>

Here is Step 6

C:\>copy C:\MySQL_5.5.12\data\test\rolando.MYD C:\MySQL_5.5.12\data\test\pamela.MYD
        1 file(s) copied.

C:\>

Here are the rest of the Steps starting at Step 7

mysql> repair table pamela;
+-------------+--------+----------+------------------------------------+
| Table       | Op     | Msg_type | Msg_text                           |
+-------------+--------+----------+------------------------------------+
| test.pamela | repair | warning  | Number of rows changed from 0 to 2 |
| test.pamela | repair | status   | OK                                 |
+-------------+--------+----------+------------------------------------+
2 rows in set (0.03 sec)

mysql> select count(1) from pamela;
+----------+
| count(1) |
+----------+
|        2 |
+----------+
1 row in set (0.00 sec)

mysql> insert into pamela (name,id) values ('carlik',3);
Query OK, 1 row affected (0.00 sec)

mysql> select * from pamela;
+-----------+----+
| name      | id |
+-----------+----+
| dominique |  1 |
| diamond   |  2 |
| carlik    |  3 |
+-----------+----+
3 rows in set (0.00 sec)

mysql>

Dangerous game, isn't it ???

Guess what? Stuff like this is actually published in "High Performance MySQL : Optimization, Backups, Replication, and more", Pages 146-148 under the Subheading Speeding Up ALTER TABLE. Page 147 Paragraph 1 says:

The technique we are about to demonstrate is unsupported, undocumented, and may not work. Use it at your risk. We advise you to back up you data first!

I also had an earlier post when someone ask a similar question : Can I rename the values in a MySQL ENUM column in one query?

You got guts, @atxdba !!!

You could use a trigger. The key problem there though is that it will have to do a lookup and so multiple concurrent inserts into the table may get messy (concurrent being within the life of the transaction).

A real alternative here is probably going to go with a natural candidate key (multiple columns of actual rather than artificial data) and add a single autoincrement key for easy joins. Having a single column reference makes joins to the table a lot easier.

Those probably aren't the answers you want to hear but they should work. If they won't work, then the question is why and what data modelling scenario you are trying to address.