Speed up test db transactions with optimized-ish SQL queries!

fast_spec_helpers.rb

def clean!(*classes)
  execute!(classes.map { |klass| "DELETE FROM #{klass.table_name}" }.join('; '))
end

def create!(klass, keys, values)
  query = make_mass_query(klass, keys, values)
  execute!(query).map { |row| klass.new(row) }
end

private

def execute!(query)
  ActiveRecord::Base.connection.execute(query)
end

def make_mass_query(klass, keys, values)
  "WITH rows AS (INSERT into #{klass.table_name} (#{keys.join(', ')})
  VALUES #{values.map { |*vals| "(#{escape_values(vals)})"}.join(', ')} RETURNING *) SELECT * FROM rows"
end

def escape_values(vals)
  vals.map do |val|
    if val.is_a?(Array)
      escape_values(val)
    elsif val.is_a?(Fixnum)
      val
    else
      "'#{val}'"
    end
  end.join(', ')
end

A friend and former colleague of mine has a gem, activerecord-import, that might help, especially for larger sets of data.