Rails: How to get PostgreSQL version being used
To check the currently running PG version from your Rails application (e.g. Rails console on your production server), simply do this:
ActiveRecord::Base.connection.select_value('SELECT version()')
Related cards:
MySQL: How to create columns like "bigint" or "longtext" in Rails migrations, and what :limit means for column migrations
Rails understands a :limit options when you create columns in a migration. Its meaning depends on the column type, and sometimes the supplied value.
[The documentation](http://apidock.com/rails/ActiveRecord/ConnectionAdapters/TableDefinition/co...
How to make changes to a Ruby gem (as a Rails developer)
At makandra, we've built a few gems over the years. Some of these are quite popular: spreewald (> 1M downloads), active_type (> 1M downloads), and geordi (> 200k downloads)
Developing a Ruby gem is different from developing Rails applications, w...
Upgrading Cucumber and Capybara to the latest versions available for Rails 2
Specify these gem versions in your Gemfile:
gem 'cucumber', '~> 1.3.0'
gem 'cucumber-rails', '= 0.3.2' # max version for Rails 2
gem 'capybara', '< 2' # capybara 2+ requires Rails 3
gem 'mime-types', '< 2' # dependeny of capybara
...
PostgreSQL vs. Rails migration: How to change columns from string to integer
When writing Rails migrations to convert a string column to an integer you'd usually say:
change_column :table_name, :column_name, :integer
However, PostgreSQL will complain:
PG::DatatypeMismatch: ERROR: column "column_name" cannot...
Rails: How to get the ordered list of used middlewares
Rails middlewares are small code pieces that wrap requests to the application. The first middleware gets passed the request, invokes the next, and so on. Finally, the application is invoked, builds a response and passes it back to the last middlew...
Rails and Postgres: How to test if your index is used as expected
This is a small example on how you can check if your Postgres index can be used by a specific query in you Rails application. For more complex execution plans it might still be a good idea to use the same path of proof.
1. Identify the...
How to write modular code
Or: How to avoid and refactor spaghetti code
Please note that I tried to keep the examples small. The effects of the methods in this card are of course much more significant with real / more complex code.
What are the benefits of more modular ...
PostgreSQL: How to add/remove/modify array values (and how to replace 1 value with multiple values)
PostgreSQL's array data type is pretty useful, but manipulating values of arrays can be awkward because of its syntax.
Consider the following users table which each example below will sta...
How to query PostgreSQL's json fields from Rails
PostgreSQL offers a really handy field type: json. You can store any JSON there, in any structure.
While its flexibility is great, there is no syntactic sugar in Rails yet. Thus, you need to manually query the database.
Demo
# Given a...
How to make Rational#to_s return strings without denominator 1 again
The way Rational#to_s works on Ruby has changed from Ruby 1.9 on. Here is how to get the old behavior back.
You may want this for things where Rationals are being used, like when subtracting Date objects from one another.