Archive for February, 2010

Dumping InnoDB tables without causing the slave to fall behind

Sunday, February 28th, 2010

Use a combination of non-locking table arguments for mysqdlump and the “nice” command to give mysqldump lower priority over other processes.

bash# nice -n 19 mysqldump --single-transaction --quick -uroot -p app3 > app3.2010022801.sql

–single-transaction doesn’t lock the tables when they are being dumped (by default -lock-tables would be enabled)

nice is a Unix command to tweak the priority of a process, from -20 (highest priority) to 19 (lowest priority)

You also probably want to compress the file to speed up transfer across the network to a backup server:

bash# tar -czvf app3.2010011801.sql.tar.gz app3.2010011801.sql

Using nice on complex queries that would actually eat up all the CPU works for every SQL query, not only mysqldump.
If you have such a complex query, instead of trying to run it from inside a mysql shell, run it from the bash as follows:

bash# nice -n 19 mysql -e "use mydb; select * from purchase where id in (select id from users where sex='female');"

… and compare with running it directly from the mysql prompt.

This is particularly handy for complex queries using JOINs between big tables.

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Working ‘Become a fan’ button directly in Facebook apps

Saturday, February 6th, 2010

Until recently you could only put up a link to the application page and hope people would find the ‘Become a fan’ at the top button themselves.

Facebook was not providing a working button the way the ‘Add Bookmark’ button works.

Here’s the indirect way to do it, using Facebook Connect:

<fb:iframe scrolling="no" frameborder="0"
   src="http://www.facebook.com/connect/connect.php?id=4563146243&connections=0&stream=0&css=http://example.com/fan.css"
   allowtransparency="true" style="border: 0px solid #cccccc; width: 113px; height: 25px; ">
</fb:iframe>

And your fan.css file should look like this:

.profileimage {
    display: none !important;
}

.name_block {
    display: none !important;
}

div {
    margin: 0px !important;
    padding: 0px !important;
}

The CSS is here to hide the app profile picture. If you want the picture to be displayed then just don’t use the CSS.

Source

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Timing your scripts

Monday, February 1st, 2010 
$start_time = microtime(true);
<...insert code to time here...>
$stop_time = microtime(true);
$time_diff = $stop_time - $start_time;
echo "Script took $time_diff seconds to execute";
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