rake files for postgres support

postgres.rake

#
# This patch makes structure dump a first class citizen
#
puts "WARN: We are patching rake tasks to support postgres.  You have upgraded Rails and may not need this patch any more (lib/tasks/postgres.rake)." if Rails.version > "3.0.9"

Rake.application.remove_task('db:schema:dump')
Rake.application.remove_task('db:schema:load')

namespace :db do
  namespace :schema do
    desc "Create a db/schema.rb file that can be portably used against any DB supported by AR"
    task :dump => :environment do
      case ActiveRecord::Base.schema_format
      when :ruby
        require 'active_record/schema_dumper'
        File.open(ENV['SCHEMA'] || "#{Rails.root}/db/schema.rb", "w") do |file|
          ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
        end
        Rake::Task["db:schema:dump"].reenable
      when :sql
        Rake::Task["db:structure:dump"].invoke
      else
        raise "That schema_format (#{ActiveRecord::Base.schema_format}) is not currently supported."
      end
    end

    desc "Load a schema.rb file into the database"
    task :load => :environment do
      case ActiveRecord::Base.schema_format
      when :ruby
        file = ENV['SCHEMA'] || "#{Rails.root}/db/schema.rb"
        if File.exists?(file)
          load(file)
        else
          abort %{#{file} doesn't exist yet. Run "rake db:migrate" to create it then try again. If you do not intend to use a database, you should instead alter #{Rails.root}/config/application.rb to limit the frameworks that will be loaded}
        end
      when :sql
        Rake::Task["db:structure:load"].invoke
      else
        raise "That schema_format (#{ActiveRecord::Base.schema_format}) is not currently supported."
      end
    end
  end

  namespace :structure do
    desc "Load the database structure from an SQL file"
    task :load => :environment do
      file = File.join(Rails.root, 'db', 'development_structure.sql')
      if File.exists?(file)
        IO.readlines(file).join.split("\n\n").each do |sql_statement|
          ActiveRecord::Base.connection.execute(sql_statement)
        end
      else
        abort %{#{file} doesn't exist yet. Run "rake db:migrate" to create it then try again. If you do not intend to use a database, you should instead alter #{Rails.root}/config/boot.rb to limit the frameworks that will be loaded}
      end
    end
  end


  # 
  # This patch ensures db:drop can work by killing the postgres connections
  # see: http://stackoverflow.com/questions/2369744/rails-postgres-drop-error-database-is-being-accessed-by-other-users
  #
  desc 'kills connections to postgres db'
  task :kill_postgres_connections => :environment do

    db_name = "#{File.basename(Rails.root)}_#{Rails.env}"
    puts "WARN: killing connections to #{db_name}."
    sh = <<EOF
ps xa \
  | grep postgres: \
  | grep #{db_name} \
  | grep -v grep \
  | awk '{print $1}' \
  | xargs kill
EOF
    puts `#{sh}`
  end
  task "db:drop" => :kill_postgres_connections
end