We had a simple request at work to make a database field case-insensitive. Which is all to say, we had to make this touch field’s once defaultly true case sensitivity:

validates_uniqueness_of :a_touchy_field

into a blatant lie:

validates_uniqueness_of :a_touchy_field, :case_sensitive => false

And this is why Rails is so great. We’re done!

BUT WAIT. WHAT ABOUT THE BIG TROUBLE?

Oh right! Well, this field is very touchy. Touchy like… millions of rows touchy. And it didn’t like all this insensitivity we we’re giving it. And neither did MySQL. There’s a lighthouse ticket all about it.

The issue is that to keep things DB-neutral, Rails is having MySQL perform a LOWER() on that field on each row to do a binary comparison for the uniqueness validation. How unkind to our conveniently indexed database field.

By default, MySQL does a case-insensitive string comparison. So we rolled our own uniqueness validation…

def TouchyModel < ActiveRecord::Base
  validate :ensure_unique_case_insensitive_touchy_field

  def ensure_unique_case_insensitive_touchy_field
    if new_record? || a_touchy_field_changed?
      if TouchyModel.exists?(:a_touchy_field => a_touchy_field)
        errors.add(:a_touchy_field, "must be alone, or else it'll get whiny")
      end
    end
  end
end

This lets us tip-toe around the call to LOWER() and get on with our validations using the default MySQL comparison.

Jamie Zawinski’s backup PSA is my favorite document about backing up data. So I ordered one of the new hybrid drives mentoned on Coding Horror and got it in the mail a few days ago.

I’ve copied disks using dd in the past, but it’s silent output always leaves me concerned. This time I went with Clonezilla Live, a simple-to-use Debian-based live CD whose sole purpose is to duplicate disks. Easy!

My next little hurdle was when I put in my hybrid drive and put the old drive into an external enclosure. My machine booted fine, but when I plugged in the external disk, it wouldn’t mount. Ubuntu 10.10 was attempting to mount the external disk to the root of the filesystem. This line in /etc/fstab was the culprit:

# <file system>  <mount point>   <type>  <options>         <dump>  <pass>
# / was on /dev/sda1 during installation
UUID=<some-uuid> /               ext4    errors=remount-ro 0       1

The first change I had to make was to change the UUID on the external disk. I used the following command to do so:

tune2fs -U random /dev/sdb1

Then, I updated the fstab like so:

# <file system> <mount point>   <type>  <options>                         <dump>  <pass>
UUID=<new-uuid> /media/backup   ext4    user,nobootwait,errors=remount-ro 0       2

The external now mounts to /media/backup, is mountable automatically by ubuntu since the user option is set, and fsck will check the drive last since pass is now set to 2. nobootwait prevents the machine from booting if the disk is not present.

I dropped this in a file, and now I have an easy command to backup to a bootable drive!

#!/bin/sh
sudo rsync -vaxE --delete --ignore-errors / /media/backup/

Adding the CCK content field to the “Sort Criteria” gave no change in the SQL query. I struggled with this for a good hour before deciding to create my view from scratch.

Once I recreated the view, I found that sorting by columns is handled in the table style settings. The not correctly sorted view was using the table style; I went back to my original view’s table settings and was able to sort by other columns by default.

Don’t Change Product’s Display Field “Image”

Well, you can if you know what you’re doing. But I had mistakenly updated the display fields for the product content type at Home › Administer › Content management › Product › Display Fields to be ‘product_full image linked to image’ for ‘full node’. The reason I shouldn’t have done this is because UberCart handles the images itself. Head over to Home › Administer › Store administration › Configuration › Product Settings to choose a Product Image Widget.

None available? Install one off the Lightbox2 or Thickbox modules to have an option.

Uploading Multiple Images

Oh! the pains of learning. Months ago I attempted to add another Image field to the Product content type. It led nowhere and took up a lot of my time. Today I learned that the CCK Image Field offers the option of multiple images. Simple!

Head over to Home › Administer › Content management › Product › Manage Fields › Image. Under “Global Settings” there is an option for number of images to allow.

Contemplates for UberCart Products

Now: my image fields are hidden from the product pages. I have an image widget set for UberCart. I’m using the Contemplate module for product node rendering. How do I show the image widget?

There is probably a better way, but I found it by using the get_defined_vars() function. Reviewing the output of that function from my product node template revealed the image widget to be in $content['image']['#value']. I dropped that in the template and had the lightbox triggering widget showing all product images.

For easier review of get_defined_vars output, install the Devel module, and use this line of code:

<?php dpm(get_defined_vars()); ?>

7 Iterations of the Carpet

To generate the carpet, take a square. Divide it into nine squares (3×3) and remove the center one. Then, for each of the remaining 8 squares, repeat ad infinitum.

If you get bored doing it an infinite number of times, take a break and eat Sierpinski’s Cookie.

The Code – SierpinskisCarpenter.py

Sorry for the crappy box this is in. Copy and paste for reading.

#!/usr/bin/python

#
# SierpinskisCarpenter.py
#
# Author: Dibson T Hoffweiler 
# WWW:    http://www.dibson.net/
#
#             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
#                     Version 2, December 2004
#
#  Everyone is permitted to copy and distribute verbatim or modified
#  copies of this license document, and changing it is allowed as long
#  as the name is changed.
#
#             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
#    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
#
#   0. You just DO WHAT THE FUCK YOU WANT TO.
#

import Image

class SierpinskisCarpenter:

    def __init__(self):
        """ Prepare the Carpenter """
        self.color = (0, 0, 255)

    def getCounter(self):
        """ Return current counter value, increment it. """
        c = self.counter
        self.counter += 1
        return c

    def getFrameFilename(self):
        """ Return filename for next frame. """
        return "carpet-frame-%02d-%06d.gif" % (self.itr_start, self.getCounter())

    def getCarpetImage(self, itr, size, init=True):
        """ Return an image object of Sierpinski's Carpet

            itr - int - how many iterations deep to go
            size - int - width of carpet in pixels
            init - bool - if True, clear counters - must set False when recursing! (default True)
        """

        if (init):
            # Prepare to lay the carpet out
            self.counter = 0

        if (0 == itr):
            # No need to iterate, return the part
            part = Image.new("RGB", (size, size), self.color)
            return part
        else:
            # Get smaller carpet, and paste it in 8 times

            third = size / 3

            partSmall = self.getCarpetImage(itr - 1, third, False)

            im = Image.new("RGB", (size, size), (255, 255, 255))

            # top left
            tl_start = (0, 0)
            im.paste(partSmall, tl_start)

            # top center
            tc_start = (third, 0)
            im.paste(partSmall, tc_start)

            # top right
            tr_start = (2 * third, 0)
            im.paste(partSmall, tr_start)

            # middle right
            mr_start = (2 * third, third)
            im.paste(partSmall, mr_start)

            # bottom right
            br_start = (2 * third, 2 * third)
            im.paste(partSmall, br_start)

            # bottom center
            bc_start = (third, 2 * third)
            im.paste(partSmall, bc_start)

            # bottom left
            bl_start = (0, 2 * third)
            im.paste(partSmall, bl_start)

            # middle left
            ml_start = (0, third)
            im.paste(partSmall, ml_start)

            return im

    def animateCarpet(self, itr, size, start=None):
        """ A recursive function to generate an animation of drawing Sierpinski's Carpet.

        - itr - int - how many iterations to do
        - size - int - image size will be a square with lengths this many pixels
        - start - 2dim tuple - top left corner of carpet to draw

        Example:

          sc = SierpinskisCarpenter()
          itr = 3
          size = (3 ** itr, 3 ** itr)
          im = sc.animateCarpet(itr, size)
          im.show()

        """

        if (None == start):
            # Init the animation
            start = (0,0)
            self.counter = 0
            self.im = Image.new("RGB", (size, size), (255, 255, 255))
            self.itr_start = itr
            self.im.save(self.getFrameFilename())

        # tab for clean debug output
        tab = "\t" * itr

        #print tab + "MAKE CARPET ITR %s" % (itr)
        #print "%sStart %s" % (tab, start)

        if (0 == itr):
            # LAST ITERATION - PAINT IT!
            #print "%sPAINTING: Start %s" % (tab, start)
            self.im.paste(self.color, (start[0], start[1], start[0] + size, start[1] + size))
            self.im.save(self.getFrameFilename())
        else:
            # NEED TO ITERATE, DO ALL 8 SQUARES

            third = size / 3

            # top left
            tl_start = (start[0], start[1])
            self.im = self.animateCarpet(itr-1, size/3, tl_start)

            # top center
            tc_start = (start[0] + third, start[1])
            self.im = self.animateCarpet(itr-1, size/3, tc_start)

            # top right
            tr_start = (start[0] + 2 * third, start[1])
            self.im = self.animateCarpet(itr-1, size/3, tr_start)

            # middle right
            mr_start = (start[0] + 2 * third, start[1] + third)
            self.im = self.animateCarpet(itr-1, size/3, mr_start)

            # bottom right
            br_start = (start[0] + 2 * third, start[1] + 2 * third)
            self.im = self.animateCarpet(itr-1, size/3, br_start)

            # bottom center
            bc_start = (start[0] + third, start[1] + 2 * third)
            self.im = self.animateCarpet(itr-1, size/3, bc_start)

            # bottom left
            bl_start = (start[0], start[1] + 2 * third)
            self.im = self.animateCarpet(itr-1, size/3, bl_start)

            # middle left
            ml_start = (start[0], start[1] + third)
            self.im = self.animateCarpet(itr-1, size/3, ml_start)

        return self.im

cm = SierpinskisCarpenter()

# EXAMPLE: saves 6 iterations of Sierpinski's Carpet
#topItr = 6
#size = 3 ** topItr
#for itr in range(topItr+1):
#    im = cm.getCarpetImage(itr, size)
#    im.save("carpet-%spx-%s.gif" % (size, itr))

# EXAMPLE: dumps out frames for drawing out carpet
#cm.animateCarpet(3, 27)