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| importance of a INDEX in mysql |
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Posted by: hijinks - 2005-03-10, 02:26 PM - Forum: LAMP
- No Replies
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A lot of people that are getting into PHP are also getting into mysql for the first time. Generally they can build a database and create a good app that works. I have seen a lot of popular scripts that don't use a index on their tables. A index in mysql is kind of like a table of contents in a book. It helps mysql find what its looking for faster.
Generally a INDEX should be placed on a column in a table that is going to be searched a lot. So for examle I have made a test table and filled it with random data. I have a column called id which should be unique to each user. So this is a key example of a column that would be used in a where section of a query often. Like this
SELECT * FROM test WHERE id=5432;
For now we won't limit it since I want to show how fast a index can make a query. So for this example I have a table called test that I have filled with close to 900k rows. Here is a query I'm doing to try to pull a row from a table with no index's.
Code: mysql> select count(*) from test where id=3232301;
+----------+
| count(*) |
+----------+
| 1 |
+----------+
1 row in set (5.97 sec)
So that query took almost 6 seconds to run. Just think you created this great forum software and someone that downloaded your forum has a killer forum that has 500k posts. So each time you need to load a page it could take 4 seconds of CPU time per request. Thats A LOT of time. Your server load will shoot through the roof and some people will begin to timeout on their connections.
So lets alter this table and set the column id to be a index.
Code: mysql> ALTER TABLE test ADD INDEX(id);
Query OK, 853614 rows affected (48.27 sec)
Records: 853614 Duplicates: 0 Warnings: 0
Ok so now lets run our same query as before and see the speed increase;
Code: mysql> select count(*) from test where id=3232301;
+----------+
| count(*) |
+----------+
| 1 |
+----------+
1 row in set (0.07 sec)
WOW.. we are WAY below the close to 6 second query time. Now that is fast.. so people if you are created a webapp that uses mysql and expect to have a load of rows in a table USE INDEX's!
As a admin I'm sick of fixing people's mistakes cause its their bad database design that's killing server's i work on.
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| Some questions |
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Posted by: NeXz - 2005-03-10, 09:20 AM - Forum: How Do I?
- Replies (6)
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1. How do I can enter the resolv.conf? With su - ? what is the command to read/edit?
You must edit resolv.conf to find the linux with a windows XP? And how do I add the linux to a members group like in windows.
2. I cant find my second harddrive in linux. I have maked the a partition with Linux format. But I dont find it eny way. I think i have to add something in a file. A command line or something. But dont know what it is :)
Thanks for the help peoples :)
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| linux-noob member photos ! |
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Posted by: anyweb - 2005-03-08, 10:36 PM - Forum: Hello
- Replies (45)
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ok then, we all talk to each other mostly live on #linux-noob (efnet server on IRC)
and of course here,
so how about showing everyone what you look like !
mine is easy, thats me <----- in the pic (avatar)
cheers
anyweb
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| how should i make my new partition table |
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Posted by: quannum - 2005-03-07, 10:20 PM - Forum: Filesystem Management
- Replies (4)
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Hello people,
do you have any suggestion what i need to change for an optimal partition table ?
current partition table:
Disk /dev/hda: 82.3 GB, 82348277760 bytes
255 heads, 63 sectors/track, 10011 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/hda1 * 1 793 6369741 83 Linux
/dev/hda2 794 859 530145 82 Linux swap
/dev/hda3 860 10011 73513440 83 Linux
hda1 i use for the fedora core 3 system.
hda3 is my swap partition.
hda3 i use for mp3,movie etc.
do you have any suggestion what i need to change for an optimal partition table ?
thank you for reading and replays if..
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| Setup an OpenLDAP network |
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Posted by: xDamox - 2005-03-07, 12:59 PM - Forum: Polls
- Replies (3)
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In the summer would anyone be interested in setting up a LDAP server over the
internet and link all the machine togther to create a LDAP network which could have.
We could mess with authentacation, setting up emails etc all that :)
We could document each stage and post it here on the message board for
people to learn form. It would be a cool little project.
Would anyone be interested??
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| Unix Scripts ? |
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Posted by: sniffy - 2005-03-07, 10:59 AM - Forum: How Do I?
- Replies (3)
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Hi @ll,
need help in scripting.
I want to start every our a ipcs -a command and the output shall be stored in a sema.txt file. After every hourly command a new txt file should be created.
Where can i learn this ???
Cu,
Sniffy
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| Setting up a Wireless card |
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Posted by: xDamox - 2005-03-05, 05:37 PM - Forum: Tips and Tricks
- No Replies
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This little guide will help you install the following Wireless network card into Fedora Core 3 :)
Code: card "ATMEL 11 Mbps Wireless RFMD PCMCIA Card"
card "ATMEL 11 Mbps Wireless 504 PCMCIA Card"
card "ATMEL 11 Mbps Wireless 504A PCMCIA Card"
card "ATMEL 11 Mbps Wireless 504+2958 PCMCIA Card"
card "ATMEL 11 Mbps Wireless RFMD Revision D PCMCIA Card"
card "ATMEL 11 Mbps Wireless RFMD Revision E PCMCIA Card"
card "Sitecom WLAN-011"
card "Belkin F5D6020"
card "3Com 3CRWE62092B 11Mbps WLAN PC Card"
card "3Com 3CRSHPW_96 Wireless LAN PC Card"
card "SMC 2632W V2 11Mbps 802.11b WLAN Card"
card "SMC 2632W V3 11Mbps 802.11b WLAN Card"
card "Actiontec 802CAT1"
card "BT Voyager 1020"
card "Siemens Gigaset PC Card II"
card "CNet CNWLC-811ARL"
card "Planet WL-3552"
card "OEM 11Mbps WLAN PCMCIA Card"
card "11WAVE WaveBuddy RFMD Revision E PC Card"
card "LG LW2100N 11Mbps WLAN PCMCIA Card"
The first set to installing your card is to check that it can be picked up the hardware. issue
the following command
You should get a response back similar to the following
Code: Socket 0:
product info: " ", "WCard"
manfid: 0xd601, 0x0007
function: 6 (network)
Once that is done you can download the atmel drivers from [/url][url=http://thekelleys.org.uk/atmel/]http://thekelleys.org.uk/atmel/
download the Fedora core 3 version and do rpm -i <package.rpm>
once that is done restart the pcmcia by issueing the following
Code: /etc/init.d/pcmcia restart
once that is done do tail /var/log/messages you shoul see your wireless card as shown below:
Code: Mar 5 16:45:25 localhost kernel: eth1: Atmel at76c50x wireless. Version 0.96 simon@thekelleys.org.uk
Mar 5 16:45:25 localhost kernel: eth1: Sitecom WLAN-011 index 0x01: Vcc 3.3, irq 3, io 0x0100-0x011f
Well thats it hope this helps you :)
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