How to name RSpec describe blocks for methods

So far our convention has been

  describe :method_name do 
    ...
  end

But this has some obvious drawback like separation of instance/class methods.
I hope we can now all agree on the unambiguous convention Mr Heinrich found in a great rspec presentation:

use “description” for non-methods
use pound “#method” for instance methods
use dot “.method” for class methods

This also makes prettier specdoc output 🙂

MySql: 4 ways to lower the impact of TEXT columns

Starting point

Normally there is a table with some small stuff like id/type/xxx_id(~50B) and a text column(default 768B + x) that is not needed all the time, because most users enter less than 255 chars or most queries only need the smaller columns.

text bloats table size
text makes queries slow
text bloats mysql query cache
text is always loaded into buffer pool (consumes ram)

Alternative Row format

With row ROW_FORMAT=DYNAMIC those default 768B+x can be reduced to a mere default 20B+x, but requires innodb_file_format=Barracuda.

1 to 1 Relationship

Keep all small columns on the first model and pull in the text from another model e.g. using translated_attributes.
Generates some overhead in the model but is reasonably fast.

Varchar column as cache + 1 to 1 Relationship

Only fetches the text/adds the relationship when needed. Useful when only a few texts are larger then 255 chars and the content is often needed. e.g. on original model:

def text_truncated(to=255)
  text = if to > 255 and text_cache.size == 255
    1_to_1_relationship.text
  else
    text_cache
  end
  text.truncate(to)
end

(this needs truncate on string)
And e.g. in the UI the text could always show truncated to 255 chars and only on click it is really loaded from the db.

Using covering index

Make an index that covers all the normal columns except the text, and FORCE INDEX on the queries.

Performance

Source:
A lot more details on the 1-to-1-relation ship / covering index can be found here

Converting String to Tempfile for file interfaces

Usage

result = Tempfile.string_as_file("id,name\n1,foo\n2,bar") do |file|
  FasterCSV.foreach(file) do |row|
    ....
  end
end

Code

class Tempfile
  def self.string_as_file(string)
    result = nil
    Tempfile.open('foo') do |f|
      f.print string
      f.close
      result = yield(f.path)
    end
    result
  end
end

Fixing Rails nested attributes on collections with sti

user.persons.build(:type=>’Manager’).class != Manager, which makes a lot of problems with single table inheritance, especially when dealing with accepts_nested_attributes_for / fields_for that rely on correct class of the associated.

# Make build associations have their given type
# Makes that: user.persons.build(:type=>Manager).class == Manger
class ActiveRecord::Reflection::AssociationReflection
  def build_association(*options)
    if options.first.is_a?(Hash) and options.first[:type].presence
      options.first[:type].to_s.constantize.new(*options)
    else
      klass.new(*options)
    end
  end
end

rails issue

Installing MongoDb on Ubuntu Hardy from source with init.d and data dir

After setting up mongo by hand for 2 servers that are not deployed via puppet, here is a bash script to do it…

sudo su root


cd /opt/ && /usr/bin/curl -OL http://downloads.mongodb.org/linux/mongodb-linux-x86_64-1.4.1.tgz && tar -zxvf mongodb-linux-x86_64-1.4.1.tgz && ln -s /opt/mongodb-linux-x86_64-1.4.1 /opt/mongodb
useradd mongod -u 5005
curl http://gist.github.com/raw/413433/834a3d0ecc96cb36f8918f6d01b65fc082025cc0/gistfile1.sh > /etc/init.d/mongodb
chown mongod:mongod /etc/init.d/mongodb

chmod 750 /etc/init.d/mongodb
mkdir /etc/mongodb

chown mongod:mongod /etc/mongodb

chmod 750 /etc/mongodb
echo "dbpath=/opt/mongodb-data/" > /etc/mongodb/mongodb.conf

chown mongod:mongod /etc/mongodb/mongodb.conf

chmod 750 /etc/mongodb/mongodb.conf

mkdir /opt/mongodb-data chown mongod:mongod /opt/mongodb-data chmod 750 /opt/mongodb-data

Michael Grosser, the Blog

Menu