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From:Stefan Hinz Date:January 17 2003 2:35pm
Subject:Re: Avg_row_length
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Gerald,

> >>(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.

Alright, I take this as a Windows goodie (my MySQL 4.0.7 runs on Win2K
;-)

Regards,
--
  Stefan Hinz <hinz@stripped>
  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: "gerald_clark" <gerald_clark@stripped>
To: "Stefan Hinz" <hinz@stripped>
Cc: "Sergei Golubchik" <serg@stripped>; "Keith C. Ivey"
<keith@stripped>; <mysql@stripped>
Sent: Friday, January 17, 2003 3:48 PM
Subject: Re: Avg_row_length


>
>
> 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 <hinz@stripped>
> >  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" <serg@stripped>
> >To: "Stefan Hinz" <hinz@stripped>
> >Cc: "Keith C. Ivey" <keith@stripped>; <mysql@stripped>
> >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 <hinz@stripped>
> >>>  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 <serg@stripped>
> >> / /|_/ / // /\ \/ /_/ / /__  MySQL AB, http://www.mysql.com/
> >>/_/  /_/\_, /___/\___\_\___/  Osnabrueck, Germany
> >>       <___/
> >>
> >>
> >
> >
> >
> >
> >
>
>

Thread
Avg_row_lengthStefan Hinz14 Jan
  • RE: Avg_row_lengthJennifer Goodie15 Jan
  • Re: Avg_row_lengthSteve Edberg15 Jan
  • Re: Avg_row_lengthDan Nelson15 Jan
  • Re: Avg_row_lengthStefan Hinz15 Jan
    • Re: Avg_row_lengthSteve Edberg15 Jan
    • Re: Avg_row_lengthKeith C. Ivey15 Jan
      • Re: Avg_row_lengthStefan Hinz16 Jan
        • Re: Avg_row_lengthKeith C. Ivey16 Jan
          • Re: Avg_row_lengthStefan Hinz16 Jan
            • Re: Avg_row_lengthSergei Golubchik16 Jan
            • Re: Avg_row_lengthZak Greant16 Jan
          • Re: Avg_row_lengthgerald_clark16 Jan
          • Re: Avg_row_lengthStefan Hinz16 Jan
            • Re: Avg_row_lengthSergei Golubchik17 Jan
            • Re: Avg_row_lengthRoger Baklund17 Jan
          • Re: Avg_row_lengthgerald_clark17 Jan
          • Re: Avg_row_lengthStefan Hinz17 Jan
  • Re: Avg_row_lengthStefan Hinz15 Jan
  • Re: Avg_row_lengthStefan Hinz15 Jan