At first I thought it was a Groovy limitation that was causing my scripts to run out of heap space when I ran them against large tables. It turned out to be the default behavior of the MySQL JDBC driver though.

By default, ResultSets are completely retrieved and stored in memory. In most cases this is the most efficient way to operate, and due to the design of the MySQL network protocol is easier to implement. If you are working with ResultSets that have a large number of rows or large values, and can not allocate heap space in your JVM for the memory required, you can tell the driver to stream the results back one row at a time.

The solution is to override three default settings. The first two override the default settings of the ResultSets that will be returned by the statement.
sql.setResultSetType( java.sql.ResultSet.TYPE_FORWARD_ONLY )
sql.setResultSetConcurrency( java.sql.ResultSet.CONCUR_READ_ONLY )

This one adds a closure that gets called every time a statement gets created.
sql.withStatement{ stmt -> stmt.setFetchSize( Integer.MIN_VALUE ) }

It’s a pretty obscure reference to this Family Guy episode:

Which is actually a reference to Mister Mxyzptlk from Superman.

I wonder which three idea balls the writers pulled out to generate that clip.

1. Persistence. If the network has an error, or I just happen to click the silly little x on my terminal window, then all I have to do is ssh back into the server and restart screen (screen -r). It will be like I never left. This means that I don’t have to worry about running everything with a nohup, and if I start a job at work I can go home and reconnect (screen -Dr) to my terminal session in order to continue monitoring the job.
2. Multiple windows. Ssh into the server, start up screen, start a job in that shell, type ‘Ctrl-a c’, and voila, a new shell in a new window. Now I can go and adjust the size and position of the windows. For instance, let’s say that I need to tail five different log files. I can start up five windows, resize and position them all on the screen, and then I’m monitoring all those files in one terminal session. I can switch back and forth between the windows by typing ‘Ctrl-a #’ where # is the number of the window, ‘Ctrl-a n’ for next, ‘Ctrl-a p’ for previous, or ‘Ctrl-a “‘ to get a list of all the windows that you can arrow up or down through. You can also rename the window you are in by typing ‘Ctrl-a A’.

Unfortunately, screen sucks straight out of the box. I recommend creating a .screenrc with these lines at a minimum:

startup_message off
shell bash

termcapinfo xterm "ks=E[?1lE:kuE[A:kd=E[B:kl=E[D:kr=E[C:kh=E[5~:kH=E[F"

caption always "%{= bb}%{+b w}%n %h %=%t %c"
hardstatus alwayslastline "%{-b gk}%-w%{+b kg}%50>%n %t%{-b gk}%+w%<"

" screen starts at window 0. These two lines make the first window 1, and
" binds 0 to window 10.
bind c screen 1
bind 0 select 10

After starting screen you should now have two lines at the bottom of your screen. The first should be blue and have the window number, name, and system time. The second should be green and have a listing of all the current windows and their names. I prefer a dark background and these colors work really well on top of black. You should review the screen manpage for more things that you can add to those status lines. One of my favorites is %l which displays the current load on the system.

Another thing that you can do with screen is create custom screenrc files for different situations. I have several that I use which automatically open certain windows for me. For instance, if I “cp .screenrc .mysqlscreenrc” and then add the following lines to the bottom of .mysqlscreenrc:

screen -t "database 1"   1 mysql -h hostname -u username -ppassword data1
screen -t "database 2"   2 mysql -h hostname -u username -ppassword data2
screen -t "localhost"    3 bash

Then, add this alias “alias mysqlscreen=’screen -S mysql -c ~/.mysqlscreenrc’”. Now all you have to do is type mysqlscreen when you log in, and it will automatically open three windows for you. Two of them will open up mysql monitor sessions, and the third will open up a shell. The -S part of the screen command names the screen session. That way if you become disconnected then a ’screen -ls’ will be more meaningful, and it will be easier to know which session is which when you do your ’screen -r’.

4:32pm up 730 days, 22:25, 231 users, load average: 0.60, 0.63, 0.69

Update: Stupid Murphy and his stupid laws. Just spent an hour working on two other machines. Only solution appeared to be rebooting both machines.

The movie is called Dnevnoy dozor, Day Watch in English. It’s the second film adapted from a series of Russian novels, and isn’t available here in the U.S. yet. However, the first movie Nochnoy dozor, Night Watch, is. After a couple of weeks of trying, the first time it arrived in the mail the disk was cracked all the way through, I finally got to watch it this weekend.

Without giving away any spoilers, the story is basically about a group of people with superhuman abilities called Others who have to decide whether they are going to be on the side of light, or on the side of dark. This all revolves around an ancient truce. Each side has their own sort of police force that monitors to ensure that the truce is being kept. The Night Watch patrols for the light side, and the Day Watch works for the dark. The interesting part of the story is that even though the Others have segregated themselves into two unique sides, it’s not cut and dried that one represents good and the other represents evil.

Night Watch is a pretty good film, especially considering it’s foreign origins. Day Watch is supposed to be released in the U.S. on June 1st. It’s going to be a limited release and I can’t find any information on whether or not it’s going to be in any theaters near here. Definitely looking forward to it though.

You’re obviously deluding yourself if you don’t agree with me.

There’s an old practical joke where people pry the keys off a keyboard and replace them out of order. A user who is not a touch typist can get really confused when they look for the right letters. The xmodmap command can be used for an excellent alternative to this prank. For example, you can add the following commands into the victim’s .bashrc file:xmodmap -e ‘keycode 91 = t T’
xmodmap -e ‘keycode 92 = s S’

This prank swaps the s and t keys on the keyboard without requiring any physical keyboard modifications. Alternately, if you can pry up and replace the keys on the keyboard, follow it up by remapping the keyboard so it actually works correctly!

Never thought of that before. Now I have no choice but to try it out.