Partial schema dumber for nullobject/rein. Supports only numerical check constraints on PostgreSQL

rein_schema_dumper.rb

module Rein::SchemaDumper
  def tables(stream)
    super
    check_constraints(stream)
  end

  def check_constraints(stream)
    constraints = @connection.execute <<-SQL
      select *
      from information_schema.check_constraints as c, information_schema.constraint_column_usage as u
      where c.constraint_name = u.constraint_name
        and c.constraint_schema = 'public'
        and u.constraint_schema = 'public'
    SQL

    if constraints.any?
      stream.puts
    end

    constraints.each do |constraint|
      table_name = constraint['table_name']
      column_name = constraint['column_name']
      check_clause = constraint['check_clause']

      case check_clause
      when /#{column_name}\s+(>=|>|=|!=|<|<=)\s+(\d+)/
        definition = case $1
                     when '>=' then 'greater_than_or_equal_to'
                     when '>'  then 'greater_than'
                     when '<=' then 'less_than_or_equal_to'
                     when '<'  then 'less_than'
                     when '='  then 'equal_to'
                     when '!=' then 'not_equal_to'
                     end
        stream.puts <<-RUBY
  add_numericality_constraint "#{table_name}", "#{column_name}", #{definition}: #{$2}
        RUBY
      end
    end
  end
end

ActiveRecord::SchemaDumper.prepend Rein::SchemaDumper