Comments on: MySQL Row & Data Limits http://rackerhacker.com/2007/01/04/mysql-row-data-limits/ Words of wisdom from a server administrator Sun, 12 Oct 2008 01:42:02 +0000 http://wordpress.org/?v=2.6.2 By: major http://rackerhacker.com/2007/01/04/mysql-row-data-limits/#comment-431 major Sun, 02 Mar 2008 15:48:33 +0000 http://fix.mhtx.net/2007/01/04/mysql-row-data-limits/#comment-431 Good points, Scott! I had forgotten about the pointer size changes in MySQL 5. Good points, Scott! I had forgotten about the pointer size changes in MySQL 5.

]]> By: scottg http://rackerhacker.com/2007/01/04/mysql-row-data-limits/#comment-430 scottg Sun, 02 Mar 2008 03:47:10 +0000 http://fix.mhtx.net/2007/01/04/mysql-row-data-limits/#comment-430 I believe all this applies only to MySQL 4 and prior versions. In MySQL 5, the default pointer size was increased to 6 bytes (48 bits), allowing for tables up to 256TB (assuming your filesystem allows files this large). The pointer can even be set to 7 bytes, allowing for a table size of up to 65,536TB. (please be patient, your backup completion time over gigabit ethernet is estimated at 16.6 years) You can check the default row pointer size with "SHOW GLOBAL VARIABLES LIKE 'myisam_data_pointer_size'; ". This will show the default pointer size in bytes. This parameter, can of course, be changed in your my.cnf if you would like a different default. Conversely, if you need to squeeze every bit of performance out of your system, you can set the row pointer size down as low as 2 bytes for tables which you are confident will never grow very large. This will save 4 bytes per row in the datafile and each index. The row pointer size of a table can be adjusted using the "ALTER TABLE" technique described in the main post. I believe all this applies only to MySQL 4 and prior versions.

In MySQL 5, the default pointer size was increased to 6 bytes (48 bits), allowing for tables up to 256TB (assuming your filesystem allows files this large). The pointer can even be set to 7 bytes, allowing for a table size of up to 65,536TB. (please be patient, your backup completion time over gigabit ethernet is estimated at 16.6 years)

You can check the default row pointer size with “SHOW GLOBAL VARIABLES LIKE ‘myisam_data_pointer_size’; “. This will show the default pointer size in bytes. This parameter, can of course, be changed in your my.cnf if you would like a different default.

Conversely, if you need to squeeze every bit of performance out of your system, you can set the row pointer size down as low as 2 bytes for tables which you are confident will never grow very large. This will save 4 bytes per row in the datafile and each index.

The row pointer size of a table can be adjusted using the “ALTER TABLE” technique described in the main post.

]]> By: Dan B http://rackerhacker.com/2007/01/04/mysql-row-data-limits/#comment-10 Dan B Tue, 14 Aug 2007 17:28:39 +0000 http://fix.mhtx.net/2007/01/04/mysql-row-data-limits/#comment-10 Why not switch the storage engine to InnoDB then you can have the same table with many rows? Why not switch the storage engine to InnoDB then you can have the same table with many rows?

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