```ruby
class GISTools < ActiveRecord::Base
  def self.length_m(geom, strategy=:rgeo)
    case strategy
    when :postgis
      # Custom SQL query without Corresponding Table
      # http://stackoverflow.com/a/1285117/19779
      sql = "select st_length(st_geomfromtext(?)::geography) as length;"
      result = self.connection.execute sanitize_sql([sql, geom.as_text])
      binding.pry
      result.first['length'].to_f
    when :rgeo
      # reference: http://daniel-azuma.com/articles/georails/part-4
      wgs84_factory = RGeo::Geographic.spherical_factory(:srid => 4326)
      geography = RGeo::Feature.cast(geom, :factory => wgs84_factory, :project => true)
      geography.length
    end
  end
end```

Add 'street_union' complex PostGIS query
user
```ruby
class GISTools < ActiveRecord::Base
  def self.length_m(geom, strategy=:rgeo)
    case strategy
    when :postgis
      # Custom SQL query without Corresponding Table
      # http://stackoverflow.com/a/1285117/19779
      sql = "select st_length(st_geomfromtext(?)::geography) as length;"
      result = self.connection.execute sanitize_sql([sql, geom.as_text])
      result.first['length'].to_f
    when :rgeo
      # reference: http://daniel-azuma.com/articles/georails/part-4
      wgs84_factory = RGeo::Geographic.spherical_factory(:srid => 4326)
      geography = RGeo::Feature.cast(geom, :factory => wgs84_factory, :project => true)
      geography.length
    end
  end

  def self.street_union
    # https://gis.stackexchange.com/questions/16698/join-intersecting-lines-with-postgis
    sql = 'select
            (st_dump(geom)).geom as geom,
            full_street_name,
            bikeway_type
          from (
            select
              st_linemerge(st_union(geom)) as geom,
              full_street_name,
              bikeway_type
            from bikeway_segments
            group by "full_street_name", "bikeway_type"
          ) as street_union'

    result = self.connection.execute sanitize_sql([sql])
    result.to_a
  end

end```
assistant