Shell Tips !

MySQL - Impact of multiple column indexes misuse

Nicolas Brousse — Wed, 13 Feb 2008 11:27:44 +0000

Here is a quick picture about the impact of MySQL indexes misuse. At work, our developers made a new release of their search engine using MySQL fulltext indexes, unfortunately they didn’t implement it correctly. The impact was a huge load on all our database servers. To find the trouble, I had to redirect the SQL search flow to a specific server and check for the slow queries then reproduce it with EXPLAIN. Don’t need a long time to find that the search query did an invalid usage of the fulltext index and the “Match / Against” syntax. In fact, the fulltext index was a multiple column fulltext index. As far as I know, it’s the same behavior for any other kind of multiple column index : You have to specify ALL the column present in your index, else index won’t be used by MySQL…

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Printing a sequence of letters or numbers

Nicolas Brousse — Mon, 14 Jan 2008 14:50:07 +0000

Some times, while scripting in your favorite shell (I mean Bash !! :) you need to print a sequence of letters or numbers. Don’t write it yourself ! Script it using seq or curly braces !

Print a sequence of number

nicolas@macvin:~$ seq 1 10

1 2 3 4 5 6 7 8 9 10

nicolas@macvin:~$ seq 0 2 10

0 2 4 6 8 10

nicolas@macvin:~$ echo {1..10}

1 2 3 4 5 6 7 8 9 10

Print a sequence of letters

nicolas@macvin:~$ echo {a..g}

a b c d e f g

Hope this will help you while doing a loop or building some hash directories :

nicolas@macvin:~$ mkdir -p test/{1..10}/{1..10}

Enjoy !

How to flush DNS Cache in Mac OS X ?

Nicolas Brousse — Thu, 03 Jan 2008 01:03:57 +0000

Joy ! I just get my new Mac Book Pro (2Go RAM / 2,4Ghz Core 2 Duo / 160Go HDD / etc.). So I’m playing a lot with VMware Fusion and multiple host (debian, ubuntu, solaris, windows, etc.) with a great fluidity ! A big improve for me who was working with an old DELL Laptop with 1Ghz Celeron and 512Mo of Ram…

But, while playing with my new laptop and my multiple virtual instances I needed to flush my DNS Cache. So, here come the tips :

With Mac OS X <= 10.4 :

macvin:~ root# lookupd -flushcache

With Mac OS X > 10.5 :

macvin:~ root# dscacheutil -flushcache

Cheap SAN and secure backup solution for small-sized platform

Nicolas Brousse — Mon, 26 Nov 2007 03:05:18 +0000

Here is a quick post about a cheap SAN and secure backup architecture solution for small-sized platform (5/10 servers). In this study case we will see how to use Network Block Devices (nbd) and soft-raid with mdadm. I design it for my personal web platform which is a small one. Last day, I was missing of free space on my backup server and I was angry by the idea to rent a most expensive server to store my backup while I had lot of unused space on my other servers.

1. Initial platform
2. New platform
3. How to do it ?

(more…)

[PHP] Zend Platform - Performance results

Nicolas Brousse — Mon, 12 Nov 2007 16:57:14 +0000

If you are a PHP developer or a LAMP server admin you probably have already heard about the Zend Platform. After some test and configure/tunning step, we deployed this solution on a heavy loaded production server running with Apache 2.x, PHP 4.4.x, MySQL Client 5.x.

(more…)