Hi!
On Aug 02, Jan Kneschke wrote:
> I have a simple table:
>
> CREATE TEMPORARY TABLE `temp_tbl` (
> `id` int(11) DEFAULT NULL
> ) ENGINE=MyISAM DEFAULT CHARSET=latin1
>
> > select * from temp_tbl;
> +------+
> | id |
> +------+
> | 1 |
> | NULL |
> | -1 |
> +------+
>
> Dumping the file I get:
>
> [0000] fd 01 00 00 00 00 00 ff 00 00 00 00 00 00 fd ff
> [0010] ff ff ff 00 00
>
> ... or unrolled:
>
> fd 01 00 00 00 00 00
> ff 00 00 00 00 00 00
> fd ff ff ff ff 00 00
>
> I would have expected to get the header-byte + 4 bytes for my INT.
>
> Even http://forge.mysql.com/wiki/MySQL_Internals_MyISAM doesn't talk about
> the trailing 00 in fixed format.
It's 5.1 ? myisam_data_pointer_size is 6 by default.
In the fixed format a record cannot be smaller than
myisam_data_pointer_size + 1.
It's for deleted chain - the first bit of the record tells if the record
is deleted, and if it is, the following myisam_data_pointer_size bytes
tell where the next deleted record is.
In dynamic format, there's no "deleted" bit, it's stored in the chunk
header instead.
Regards / Mit vielen Grüssen,
Sergei
--
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