Maximum size of a MySQL query

Unless you changed the default, this will be 16 MB:

mysql> SHOW VARIABLES WHERE Variable_name="max_allowed_packet";
| Variable_name      | Value    |
| max_allowed_packet | 16777216 |
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Asset pipeline for Rails 2

The asset pipeline from Rails 3.1 packported to 2.3. By Michael Grosser from parallel_tests fame.

Drag'n'drop in trees: I went to town

For my Gem Session project Holly I ran the Ironman of drag'n'drop implementations:

  • Dragging in nested lists
  • User-definable order of items
  • Complicated item elements with super-custom CSS and other Javascript functionality
  • Items that can be both leaves and containers of other items
  • has_ancestry on the server side

Things I learned:

  • Be ready to write a lot of CSS. You need to indicate what is being dragged, where it will be dropped, if it is dropped above, below o…
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jQuery.cssHooks – jQuery API

The $.cssHooks object provides a way to define functions for getting and setting particular CSS values. It can also be used to create new cssHooks for normalizing CSS3 features such as box shadows and gradients.

For example, some versions of Webkit-based browsers require -webkit-border-radius to set the border-radius on an element, while earlier Firefox versions require -moz-border-radius. A css hook can normalize these vendor-prefixed properties to let .css() accept a single, standard property name (border-radius, or with DOM property synt…

Updated: Check whether an element is visible or hidden with Javascript

  • Added information about what jQuery considers "visible"
  • Added a solution for Prototype
  • Added a patch for Prototype that replaces the useless Element#visible() method with an implementation that behaves like jQuery.
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Using the Rake Build Language

Rake (like make) allows you to add dependencies to a task after you've
initially declared it. Indeed it allows you to continue to talk
about a task in multiple places. This way I can decide to add
dependencies close to the pre-requisite task

When connecting to a second database, take care not to overwrite existing connections

Sometimes, you may want to open up a second database connection, to a read slave or another database. When doing that, you must make sure you don't overwrite an existing connection.

The problem

While this may look good, it will actually cause all kinds of trouble:

def with_other_database

Putting aside that you are setting the general connection here (not generally a …

Request limit of

The facebook API allows up to 600 requests per 600 seconds.
If you poll more often, you'll get no or malformed answers.

Nice way to set data attributes when creating elements with Rails helpers

You can say this in helpers like link_to and content_tag:

= link_to 'Label', root_url, :data => { :foo => 'bar', :bam => 'baz' }

This will produce:

<a href="/" data-foo="bar" data-bam="baz">Label</a>

Only works in Rails 3. In Rails 2 you do

= link_to 'Label', root_url, 'data-foo' => 'bar', 'data-bam' => 'baz' }

Updated: Capybara: Check that a page element is hidden via CSS

  • The step we used in the past (Then "foo" should not be visibile) doesn't reliably work in Selenium features.
  • I overhauled the entire step so it uses Javascript to detect visibility in Selenium.
  • The step has support for jQuery and Prototype projects, so it should be a drop-in replacement for all your projects.
  • For Rack::Test the step no longer uses XPath so you should be able to understand it when you are not a cyborg :)
  • There were some other cards detailing alternative steps to detect visibility. I deleted all these other cards s…

RubyMine: Using pinned tabs will increase your productivity

I highly recommend that you make use of RubyMine's feature to pin tabs.

When you pin all "important" files, you can follow method definitions, wildly open files from search results and have a ton of open tabs – without the problem of finding the stuff you were working on before.


  1. Pin the tabs of files that are currently in the focus of your work (important models, specs, etc):
    • Right-click a tab and select "Pin tab"
    • Or use a shortcut (see below)
  2. Work as usual.
  3. Once you opened other tabs because you searched …

When and Date.tomorrow return the same day...

… you probably have a time zone issue.

When you get"2011-11-11 00:00") do
  Time.current   => Thu, 10 Nov 2011 23:00:01 UTC +00:00       => Fri Nov 11 00:00:02 +0100 2011     => Fri, 11 Nov 2011
  Date.tomorrow  => Fri, 11 Nov 2011

you probably haven't defined a zime zone yet.

So might fix this by adding the following lines to your application.rb:

class Application < Rails::Application
  config.time_zone = 'Berlin' # or whatever your time zone
end   ...

MySQL operator precedence

Take care in queries where multiple AND or OR operators are used. In doubt, always use braces to enforce precedence.

External content

PhoneGap Build

Write your app using HTML, CSS or JavaScript, upload it to the PhoneGap Build service and get back app-store ready apps for Apple iOS, Google Android, Windows Phone 7, Palm, Symbian, BlackBerry and more.

By compiling in the cloud with PhoneGap Build, you get all the benefits of cross-platform development but can still build apps just the way you like.

How to enable MySQL query logging

This will make MySQL log all received queries so you can see for yourself what happens on the database level.

Don't switch this on for production machines!

  1. Edit your my.cnf:
    sudo vim /etc/mysql/my.cnf
  2. In the [mysqld] section, add:
  3. Restart your MySQL daemon. On Ubuntu:
    sudo service mysql restart

Note that your MySQL performance will suffer. But when you need to enable query logging for a debug fest, you probably don't care about that.

Update Skype 4.x to at least

There was a bug in Skype that could cause messages to be sent to incorrect recipients (anyone, not only people from your contact list).

If you were using Skype 4 on Linux (or Skype on any other platform), upgrade immediately.

I don't know if Skype 2 on Linux is affected.

Click on a piece of text in Cucumber / Capyabra

The step definition below lets you write:

When I click on "Foo"

This is useful in Selenium features where the element you click on is not necessarily a link or button, but could be any HTML element with a Javascript event binding.

The easiest way to get this step is to use Spreewald. If you would like to add it manually, here is the step definition:

When /^I click on "([^\"]+)"$/ do |text|
  matcher = ['*', { :text => text }]
  element = page.find(:css, *matcher)
  while be...
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