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Large Unused Tables Vs Performance


I've been working on a website with a rather large a database. One of the about 100 tables in there was about 1/4 of the total database size.

The table had no use anymore at the time I worked the website, so it was just sitting there, doing absolutely nothing. Obviously to spare diskspace we deleted the table.

But the question I have now, can unused large tables affect the perfomance of Mysql?
I've searched a bit around, but honestly I couldn't find a clear answer about it right away (maybe I haven't searched enough either :) )




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I have a table with about 100 million rows:

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[color=blue]
> SELECT count(*)[/color]
-> FROM UserSnap
-> WHERE LogDate<now() - INTERVAL 750 DAY;
+----------+
| count(*) |
+----------+
| 308969 |
+----------+
[color=blue]
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[color=blue]
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+----------+-------------+------+-----+---------------------+-------+
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+----------+-------------+------+-----+---------------------+-------+
| LogDate | datetime | | PRI | 0000-00-00 00:00:00 | |
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(I use postgresql).

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I have 4 important tables here (I'm only posting the columns which I use):

`auth`

UID mediumint(8) unsigned PRI NULL auto_increment
username varchar(32) MUL
clan_id mediumint(8) unsigned MUL 0
clan_abbrev varchar(7) MUL
`clans`


ID mediumint(8) unsigned PRI NULL auto_increment
Abbrev varchar(7) MUL
Name varchar(64)
icon_id smallint(5) unsigned 0
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UID int(10) unsigned PRI 0
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UID int(10) unsigned 0
ID int(10) unsigned PRI NULL auto_increment
Name varchar(32)
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(
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FROM `usernames` , `auth` , `clans` , `stats`
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AND auth.UID = usernames.UID
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AND stats.UID = auth.UID
)
UNION (

SELECT usernames.UID AS `UID` , usernames.Name AS `result` , auth.username AS `playername` , usernames.Uses AS `Uses` , 0 AS `clan_id` , '' AS `clan_abbrev` , '' AS `clan_name` , 0 AS `clan_icon` , stats.kills AS `kills`
FROM `usernames` , `auth` , `stats`
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AND auth.UID = usernames.UID
AND auth.clan_id =0
AND stats.UID = auth.UID
)
ORDER BY `Uses` DESC
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country

(id) country
(1) America
(2) Germany
(3) Canada
(4) China
(5) Egypt
(6) Russia
(7) Korea
(8) France
(9) Brazil

city

(id) city
(1) Berlin
(2) New York
(3) Cairo
(4) Paris
(5) Seoul
(6) Peking
(7) Chicago
(8) Moscow
(9) Denver
I have two tables like the above.


And I have one of these tables below.


message1

(id) (city) message
(1) (2) I love New York.
(2) (5) Kumkang mountains are beautiful.
(3) (4) I was born in France.
(4) (6) Great Wall is great.
(5) (7) Chicago is a big city.

message2

(id) (city) (country) message
(1) (2) (1) I love New York.
(2) (5) (7) Kumkang mountains are beautiful.
(3) (4) (8) I was born in France.
(4) (6) (4) Great Wall is great.
(5) (7) (1) Chicago is a big city.



code1

select city, country
from message1
left join city on city.id=message1.city
left join country on country.id=city.country

code2

select city, country
from message2
left join city on city.id=message2.city
left join ccountry on country.id=message2.country
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"mysqlcheck --repair dbname" over a database with only one myisam table of more than 10.000.000 rows and 5 GB. The elapsed time to repair is about 1 hour!

Is possible to increase speed?

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Low Performance With Linux SMP
I use
#mysql -V
mysql Ver 12.21 Distrib 4.0.15, for suse linux (i686)

with a SMP-kernel

When I used this version with a kernel not SMP mysql was very very fast but now
with the SMP-kernel the mysql is very very slow. I takes several minutes to make an INSERT on a table with near 50.000 Records

Is there any problem with mysql an SMP? is a problem of the version I have installed?

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Execution Performance
Just out of curiosity, does adding LIMIT 1 to the end of single row UPDATE queries improve execution speed at all?

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