PostgreSQL uses the C library's locale facilities for sorting strings:

• First, all the letters are compared, ignoring spaces and punctuation.
• It sorts upper and lower case letters together. So the order will be something like a A b B c C
• Then, spaces and punctuation are compared to break ties.

Example:

Further reading

• [PostgreSQL-FAQ: Why do my strings sort incorrectly?](h...

Converting string characters to or from their integer value (7-bit ASCII value or UTF-8 codepoint) can be done in different ways in Ruby:

• String#ord or String#unpack to get character values
• Integer#chr or Array#pack to convert character values into Strings

Character values to Strings

Integer#chr

To get the character for a 7-bit ASCII value or UTF-8 codepoint (0-127) you can use Integer#chr:

116.chr
# => "t"

To get a character for values larger than 127, you need to pass the encoding. E.g. to get codepoint 25...

As your Rails project grows, you will accumulate a number of small patches. These will usually fix a bug in a gem, or add a method to core classes.

Instead of putting many files into config/initializers, I recommend to group them by gem in lib/ext:

lib/
  ext/
    factory_girl/
      mixin.rb
    carrierwave/
      change_storage.rb
      fix_cache_ids.rb
      sanitize_filename_characters.rb
    ruby/
      range/
        covers_range.rb
      array/
        dump_to_excel.rb
        xss_aware_join.rb
      enumerable/
    ...

Helix allows you to implement performance-critical code of your Ruby app in Rust, without requiring glue code to bridge between both languages.

See attached article for a longer write-up about the why and how.

When dealing with time zones in Rails, there is one key fact to keep in mind:

Rails has configurable time zones, while
Ruby is always in the server's time zone

Thus, using Ruby's time API will give you wrong results for different time zones.

"Without" time zones

You can not actually disable time zones, because their existence is a fact. You can, however, tell Rails the only single time zone you'll need is the server's.

config.time_zone = "Berlin" # Local time zone
config.active_record.default_timezone = :loca...

This gem gives you a rake task db:seed:dump do create a db/seeds.rb from your current database state.

The generated db/seeds.rb will look this:

Product.create!([
  { category_id: 1, description: "Long Sleeve Shirt", name: "Long Sleeve Shirt" },
  { category_id: 3, description: "Plain White Tee Shirt", name: "Plain T-Shirt" }
])
User.create!([
  { password: "123456", username: "test_1" },
  { password: "234567", username: "test_2" }
])

Instead of using this hack you might want to use MariaDB 10.x which can work with both old and new apps.

An alternative could be to use the MySQL Docker image which is still updated for 5.6.

Ubuntu 16.04 only provides packages for MySQL 5.7 which has a range of backwards compatibility issues with code written against older MySQL versions.

Oracle maintains a list of official APT repositories for MySQL 5.6, but those repositories do...

Tool to show you which gems are slow to load:

➜  git:(master) ✗ bundle exec bumbler
[#################################################                             ]
(49/65) travis-lint...
Slow requires:
    110.21  render_anywhere
    147.33  nokogiri
    173.83  haml
    179.62  sass-rails
    205.04  delayed_job_active_record
    286.76  rails
    289.36  mail
    291.98  capistrano
    326.05  delayed_job
    414.27  pry
    852.13  salesforce_bulk_api

Stackprof is a sampling call-stack profile for Ruby 2.1+.

Instead of tracking all method calls, it will simply collect the current stack trace of a running program at fixed intervals. Methods that appear on top of the stack trace most often, are the methods your program spends most of its time in.

The big advantage of this is that it is very fast. You can even enable it in production and collect real performance data. See the README on how to add it as a middleware. It will dump its data to the tmp directory.

Sampling is by default base...

Uses FFI and works all relevant operating systems.

If you'd try to do it yourself, you'd have to use FFI which is a bit awkward (see the gem's code), or call commands like df -B1 and search the strings for your relevant data.
That gem takes the pain away and works nicely.

Validations should be covered by a model's spec.

This card shows how to test an individual validation. This is preferrable to save an entire record and see whether it is invalid.

Recipe for testing any validation

In general any validation test for an attribute :attribute_being_tested looks like this:

1. Make a model instance (named record below)
2. Run validations by saying record.validate
3. Check if record.errors[:attribute_being_tested] contains the expected validation error
4. Put the attribute into a valid state
5. Run...

To install gems Bundler needs to be able to talk to https://api.rubygems.org.

If you are behind a proxy you can use the https_proxy environment variable:

https_proxy=http://myproxy:123 bundle install

Note that if there is no https_proxy env variable, Bundler will also look for a http_proxy env variable.

With Capistrano

Ideally the server you're deploying on exports an https_proxy variable for all shells.

If you don't have control over the server setup, you can also add this to your Capistrano config:
...

I got this error when running Rails 2.3 tests for Rails LTS. More stacktrace:

NoMethodError: undefined method `cache' for Gem:Module
    /vagrant/rails-2-3-lts-repository/railties/lib/rails_generator/lookup.rb:212:in `each'
    /vagrant/rails-2-3-lts-repository/railties/lib/rails_generator/lookup.rb:146:in `to_a'
    /vagrant/rails-2-3-lts-repository/railties/lib/rails_generator/lookup.rb:146:in `cache'
    /opt/vagrant_ruby/lib/ruby/1.8/fileutils.rb:243:in `inject'
    /vagrant/rails-2-3-lts-repository/railties/l...

Note

The maintenance mode is enabled on all application server as soon as the file /public/system/maintenance.html is present.

Installation

Add this line to your application's Gemfile:

 gem 'capistrano', '~> 3.0'
 gem 'capistrano-maintenance', '~> 1.0'

Add this line to you application's Capfile:

require 'capistrano/maintenance'

Enable task

Present a maintenance page to visitors. Disables your application's web interface by writing a #{maintenance_basename}.html file to each web server. The servers m...

You login to a Linux server with a performance issue: what do you check in the first minute?

uptime
dmesg | tail
vmstat 1
mpstat -P ALL 1
pidstat 1
iostat -xz 1
free -m
sar -n DEV 1
sar -n TCP,ETCP 1
top

Also see:

• How to get a rough picture about a Rails project
• How to examine an unknown Ruby object

rack-mini-profiler is a powerful Swiss army knife for Rack app performance. Measure SQL queries, memory allocation and CPU time.

This should probably not be loaded in production (the article recommends otherwise), but this looks like a useful tool.

In Ruby 2.3 you can use <<~ instead of <<- to automatically remove indentation from a HEREDOCs:

str = <<~MESSAGE
  Hello Universe!
  This is me.
             Bye!
MESSAGE

str will now be:

Hello Universe!
This is me.
           Bye!

The nokogiri gem provides different packages for several platforms. Each platform-specific variant ships pre-built binaries of libxml2, e.g. x86_64-linux includes binaries for 64bit Linux on Intel/AMD. This significantly speeds up installation of the gem, as Nokogiri no longer needs to compile libxml2.

However, this also means that for each security issue with libxml2, Nokogiri maintainers have to update their pre-built binaries and release a new version of the gem. Then, you need to update and ...

E-mails are usually encoded using Quoted Printable. Here is how to decode or encode such strings.

You probably know Quoted Printable from e-mail bodies appearing in Rails logs, where =s become =3Ds in URLs, or where long lines are split up and trailed by = after each split.

Decode Quoted Printable

Decoding such strings is actually quite simple using plain Ruby:

"foo=3Dbar".unpack('M')[0]
# => "foo=bar"

Note that unpack will return an array. Our result is the 1st item.
...

Install this gem and stop using bundle exec or even Geordi's handy b. Yay!

When using Sidekiq in your application, you must write thread-safe code.

This wiki page also lists gems that are known to be unsafe on threaded applications.
When adding a gem that will also be used by a Sidekiq worker, make sure to confirm it's thread-safe.

This looks like it is safe to use:

2.2.1 :001 > a = b = "hello world"
"hello world"
2.2.1 :002 > a
"hello world"
2.2.1 :003 > b
"hello world"
2.2.1 :004 > b = " goodbye!"
" goodbye!"
2.2.1 :005 > a
"hello world"
2.2.1 :006 > b
" goodbye!"

But it isn't!

2.2.1 :010 > a = b = "hello world"
"hello world"
2.2.1 :011 > a
"hello world"
2.2.1 :012 > b
"hello world"
2.2.1 :013 > b << " goodbye!"
"hello world goodbye!"
2.2.1 :014 > a
"hello world goodbye!"
2.2.1 :015 > b
"hello world goodbye!"

What is happening when we do `a = b = ...

Cucumber raises a Cucumber::Ambiguous if more than one step definitions match a step.

Our new cucumber_priority gem provides a way to mark step definitions as overridable, meaning that they can always be overshadowed by a more specific version without raising an error.

This gem is currently used by spreewald and cucumber_factory.

Marking step definiti...