Mysql – How to add column to big table in MySQL

The biggest thing most people forget about TRUNCATE TABLE is that TRUNCATE TABLE is DDL and not DML. In InnoDB, the metadata within ibdata1 contains a numbered list of InnoDB tables. Using TRUNCATE TABLE causes the internal metadata id of the InnoDB table to shift. This happens because TRUNCATE TABLE effectively does the following:

Example: To truncate an InnoDB Table called mydb.mytb

USE mydb
CREATE TABLE newtb LIKE mytb;
ALTER TABLE mytb RENAME oldtb;
ALTER TABLE newtb RENAME mytb;
DROP TABLE oldtb;

The new mytb would thus have a different internal metadata id.

When you copied the .ibd file to some other place, the .ibd contains within it the original internal metadata id. Simply putting the .ibd file back does not cause a reconciliation of the internal metadata id with that of the one in ibdata1.

What you should have done is this:

Copy the .ibd file of the InnoDB table. Then, run this

ALTER TABLE tablename DISCARD TABLESPACE;

To bring it back later on, copy the .ibd file back into datadir and then run

ALTER TABLE tablename IMPORT TABLESPACE;

This would have preserved the internal metadata id.

Make sure .frm is always present.

I once helped a client restore 30 InnoDB tables he hosed in the same manner. I had to use another DB server and play some games with adding and dropping InnoDB tables to hunt down the correct internal metadata id.

The client found this article : http://www.chriscalender.com/?tag=innodb-error-tablespace-id-in-file . We used it and it helped a great deal. I hope it helps you.

I'm not certain. I tried to start out be reproducing your problem but the alter worked fine for me.

test > CREATE TABLE `bar` (  `content` text ) ENGINE=MyISAM DEFAULT CHARSET=latin1;  INSERT INTO bar VALUES (0x8081828384858687898A8B8C8D8E8F909192939495969798999A9B9C9D9E9F);
Query OK, 0 rows affected (0.02 sec)

Query OK, 1 row affected (0.00 sec)

test > ALTER TABLE bar CHANGE content content TEXT CHARACTER SET UTF8;
Query OK, 1 row affected (0.04 sec)
Records: 1  Duplicates: 0  Warnings: 0

test > select * from bar;
+---------------------------------+
| content                         |
+---------------------------------+
| ����������������������������� |
+---------------------------------+
1 row in set (0.00 sec)

test > set names utf8;
Query OK, 0 rows affected (0.00 sec)

test > select * from bar;
+---------------------------------------------------------------------------------+
| content                                                                         |
+---------------------------------------------------------------------------------+
| €‚ƒ„…†‡‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ |
+---------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Here's my related char settings

test > show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

Edit

My char settings before running set names utf8

test > show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

Version

test > select version();
+-------------------------+
| version()               |
+-------------------------+
| 5.1.41-3ubuntu12.10-log |
+-------------------------+
1 row in set (0.00 sec)