A patch for Rails 5 to use MySQL spatial index

abstract_mysql_adapter_patch_for_spatial_index.rb

require "active_record/connection_adapters/abstract_mysql_adapter"

# NOTE: Set SRID 0 as same as mysql's default
silence_warnings do
  GeoRuby::SimpleFeatures::DEFAULT_SRID = 0
end

module ActiveRecord
  module Type
    class Spatial < Value
      def type
        :spatial
      end

      private

      def cast_value(value)
        return value unless value.is_a?(::String)
        GeoRuby::SimpleFeatures::Geometry.from_ewkb(value[4..-1]) rescue value
      end
    end
  end
end

module AbstractMysqlAdapterPatch
  def initialize_type_map(m)
    super
    # NOTE: Only support `point` geometry data
    m.register_type %r(point)i, ActiveRecord::Type::Spatial.new
  end

  def quote(value)
    if value.is_a?(GeoRuby::SimpleFeatures::Point)
      "GeomFromWKB(0x#{value.as_hex_wkb},#{value.srid})"
    else
      super
    end
  end
end

ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter.prepend AbstractMysqlAdapterPatch