Stefan Hinz wrote:
Sergei,
any other guru who can explain why 10 = 11?
It's because of NULLs.
Extra byte is used to mark, if the column is NULL or not.
Thanks alot for the explanation. Thanks to Gerald Clark, too, who told
me the same.
(in fact it's a bitmap, that is it would be one byte for up to 8
columns, then it'll be 2 bytes, etc.)
If so, this table should have an average row length of 92, not 91,
It does on mine.
shouldn't it (9 cols * 10 bytes + 2 bytes)?
MySQL>DESCRIBE myrowisam;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| col1 | char(10) | | | | |
| col2 | char(10) | | | | |
| col3 | char(10) | | | | |
| col4 | char(10) | | | | |
| col5 | char(10) | | | | |
| col6 | char(10) | | | | |
| col7 | char(10) | | | | |
| col8 | char(10) | | | | |
| col9 | char(10) | | | | |
+-------+----------+------+-----+---------+-------+
MySQL>SELECT * FROM myrowisam;
+------+------+------+------+------+------+------+------+------+
| col1 | col2 | col3 | col4 | col5 | col6 | col7 | col8 | col9 |
+------+------+------+------+------+------+------+------+------+
| foo | foo | foo | foo | foo | foo | foo | foo | foo |
+------+------+------+------+------+------+------+------+------+
MySQL>SHOW TABLE STATUS LIKE 'myrowisam';
+-----------+--------+------------+------+----------------+
| Name | Type | Row_format | Rows | Avg_row_length |
+-----------+--------+------------+------+----------------+
| myrowisam | MyISAM | Fixed | 1 | 91 |
+-----------+--------+------------+------+----------------+
Regards,
--
Stefan Hinz <[EMAIL PROTECTED]>
Geschäftsführer / CEO iConnect GmbH <http://iConnect.de>
Heesestr. 6, 12169 Berlin (Germany)
Tel: +49 30 7970948-0 Fax: +49 30 7970948-3
----- Original Message -----
From: "Sergei Golubchik" <[EMAIL PROTECTED]>
To: "Stefan Hinz" <[EMAIL PROTECTED]>
Cc: "Keith C. Ivey" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Thursday, January 16, 2003 9:16 PM
Subject: Re: Avg_row_length
Hi!
On Jan 16, Stefan Hinz wrote:
Keith,
thanks once again! Well, anyone here from the MySQL developer team?
Or
any other guru who can explain why 10 = 11?
Here's the problem once again:
mysql> DESCRIBE myrowisam;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| col | char(10) | YES | MUL | NULL | |
+-------+----------+------+-----+---------+-------+
mysql> SHOW TABLE STATUS LIKE 'myrowisam';
+-----------+--------+------------+------+----------------+
| Name | Type | Row_format | Rows | Avg_row_length |
+-----------+--------+------------+------+----------------+
| myrowisam | MyISAM | Fixed | 109 | 11 |
+-----------+--------+------------+------+----------------+
Regards,
--
Stefan Hinz <[EMAIL PROTECTED]>
Gesch?ftsf?hrer / CEO iConnect GmbH <http://iConnect.de>
Heesestr. 6, 12169 Berlin (Germany)
Tel: +49 30 7970948-0 Fax: +49 30 7970948-3
It's because of NULLs.
Extra byte is used to mark, if the column is NULL or not.
(in fact it's a bitmap, that is it would be one byte for up to 8
columns, then it'll be 2 bytes, etc.)
Regards,
Sergei
--
MySQL Development Team
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <[EMAIL PROTECTED]>
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, http://www.mysql.com/
/_/ /_/\_, /___/\___\_\___/ Osnabrueck, Germany
<___/
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