monkeypatch active record mysql adapter to understand collation, charset

monkeypatch_ar_mysql_collation_charset.rb

# this is ugly and terrible, don't do this

module ActiveRecord
  module ConnectionAdapters
    class TableDefinition
      def column(name, type, options = {})
        name = name.to_s
        type = type.to_sym

        column = self[name] || new_column_definition(@base, name, type)

        limit = options.fetch(:limit) do
          native[type][:limit] if native[type].is_a?(Hash)
        end

        column.limit     = limit
        column.precision = options[:precision]
        column.scale     = options[:scale]
        column.default   = options[:default]
        column.null      = options[:null]
        column.collation = options[:collation]
        puts "collation: #{column.collation}" if options[:collation]
        column.charset   = options[:charset]
        self
      end
      private

      def new_column_definition(base, name, type)
        definition = AbstractMysqlAdapter::ColumnDefinition.new base, name, type
        @columns << definition
        @columns_hash[name] = definition
        definition
      end
    end

    class Table
      %w( string text integer float decimal datetime timestamp time date binary boolean ).each do |column_type|
        class_eval <<-EOV, __FILE__, __LINE__ + 1
          def #{column_type}(*args)                                          # def string(*args)
            options = args.extract_options!                                  #   options = args.extract_options!
            column_names = args                                              #   column_names = args
            type = :'#{column_type}'                                         #   type = :string
            column_names.each do |name|                                      #   column_names.each do |name|
              puts "name: #{name}"
              column = AbstractMysqlAdapter::ColumnDefinition.new(@base, name.to_s, type)          #     column = ColumnDefinition.new(@base, name, type)
              if options[:limit]                                             #     if options[:limit]
                column.limit = options[:limit]                               #       column.limit = options[:limit]
              elsif native[type].is_a?(Hash)                                 #     elsif native[type].is_a?(Hash)
                column.limit = native[type][:limit]                          #       column.limit = native[type][:limit]
              end                                                            #     end
              column.precision = options[:precision]                         #     column.precision = options[:precision]
              column.scale = options[:scale]                                 #     column.scale = options[:scale]
              column.default = options[:default]                             #     column.default = options[:default]
              column.null = options[:null]                                   #     column.null = options[:null]
              column.collation = options[:collation]                         #     column.default = options[:default]
              column.charset = options[:charset]                             #     column.null = options[:null]
              @base.add_column(@table_name, name, column.sql_type, options)  #     @base.add_column(@table_name, name, column.sql_type, options)
            end                                                              #   end
          end                                                                # end
        EOV
      end
    end

    class AbstractMysqlAdapter
      class Column < ConnectionAdapters::Column
        attr_reader :charset
      end

      class ColumnDefinition < ActiveRecord::ConnectionAdapters::ColumnDefinition
        attr_accessor :charset, :collation

        def to_sql
          column_sql = "#{base.quote_column_name(name)} #{sql_type}"
          column_options = {}
          column_options[:null] = null unless null.nil?
          column_options[:default] = default unless default.nil?
          column_options[:collation] = collation unless collation.nil?
          column_options[:charset] = charset unless charset.nil?
          add_column_options!(column_sql, column_options) unless type.to_sym == :primary_key
          column_sql
        end
      end


      def add_column_options!(sql, options)
        if options[:charset]
          sql << " CHARACTER SET #{options[:charset]}"
        end
        if options[:collation]
          puts "adding column options #{options}"
          sql << " COLLATE #{options[:collation]}"
        end
        super
      end

      private

    end
  end

  class SchemaDumper
    def table(table, stream)
        columns = @connection.columns(table)
        begin
          tbl = StringIO.new

          # first dump primary key column
          if @connection.respond_to?(:pk_and_sequence_for)
            pk, _ = @connection.pk_and_sequence_for(table)
          elsif @connection.respond_to?(:primary_key)
            pk = @connection.primary_key(table)
          end

          tbl.print "  create_table #{remove_prefix_and_suffix(table).inspect}"
          if columns.detect { |c| c.name == pk }
            if pk != 'id'
              tbl.print %Q(, :primary_key => "#{pk}")
            end
          else
            tbl.print ", :id => false"
          end
          tbl.print ", :force => true"
          tbl.puts " do |t|"

          # then dump all non-primary key columns
          column_specs = columns.map do |column|
            raise StandardError, "Unknown type '#{column.sql_type}' for column '#{column.name}'" if @types[column.type].nil?
            next if column.name == pk
            spec = {}
            spec[:name]      = column.name.inspect

            # AR has an optimization which handles zero-scale decimals as integers. This
            # code ensures that the dumper still dumps the column as a decimal.
            spec[:type]      = if column.type == :integer && [/^numeric/, /^decimal/].any? { |e| e.match(column.sql_type) }
                                 'decimal'
                               else
                                 column.type.to_s
                               end
            spec[:limit]     = column.limit.inspect if column.limit != @types[column.type][:limit] && spec[:type] != 'decimal'
            spec[:precision] = column.precision.inspect if column.precision
            spec[:collation] = column.collation.inspect if column.collation
            spec[:charset] = column.charset.inspect if column.charset
            spec[:scale]     = column.scale.inspect if column.scale
            spec[:null]      = 'false' unless column.null
            spec[:default]   = default_string(column.default) if column.has_default?
            (spec.keys - [:name, :type]).each{ |k| spec[k].insert(0, "#{k.inspect} => ")}
            spec
          end.compact

          # find all migration keys used in this table
          keys = [:name, :limit, :precision, :scale, :default, :null, :collation, :charset] & column_specs.map{ |k| k.keys }.flatten

          # figure out the lengths for each column based on above keys
          lengths = keys.map{ |key| column_specs.map{ |spec| spec[key] ? spec[key].length + 2 : 0 }.max }

          # the string we're going to sprintf our values against, with standardized column widths
          format_string = lengths.map{ |len| "%-#{len}s" }

          # find the max length for the 'type' column, which is special
          type_length = column_specs.map{ |column| column[:type].length }.max

          # add column type definition to our format string
          format_string.unshift "    t.%-#{type_length}s "

          format_string *= ''

          column_specs.each do |colspec|
            values = keys.zip(lengths).map{ |key, len| colspec.key?(key) ? colspec[key] + ", " : " " * len }
            values.unshift colspec[:type]
            tbl.print((format_string % values).gsub(/,\s*$/, ''))
            tbl.puts
          end

          tbl.puts "  end"
          tbl.puts

          indexes(table, tbl)

          tbl.rewind
          stream.print tbl.read
        rescue => e
          stream.puts "# Could not dump table #{table.inspect} because of following #{e.class}"
          stream.puts "#   #{e.message}"
          stream.puts
        end

        stream
    end
  end
end