Shell Tips !

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, in such case you have to specify ALL the column present in your index, else the index won’t be used by MySQL…

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 !

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 improvement 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