Mapnik need to know postgis column type

Mapnik need to know postgis column type to render properly. This mapnik xml for style not working for me.

 <Style name="jalan_casing2">
    <Rule>
      <Filter>[jenis] = 'lebuhraya'</Filter>
      <MaxScaleDenominator>&maxscale_zoom7;</MaxScaleDenominator>
      <MinScaleDenominator>&minscale_zoom7;</MinScaleDenominator>
      <LineSymbolizer>
        <CssParameter name="stroke">#808080</CssParameter>
        <CssParameter name="stroke-width">6</CssParameter>
        <CssParameter name="stroke-linejoin">round</CssParameter>
        <CssParameter name="stroke-linecap">round</CssParameter>
      </LineSymbolizer>
    </Rule>
  </Style>
  <Layer name="jalan_lebuhraya" srs="+proj=latlong +datum=WGS84" status="on">
    <StyleName>jalan_casing2</StyleName>
    <StyleName>jalan_fill</StyleName>
    <StyleName>jalan_text</StyleName>
    <Datasource>
      <Parameter name="type">postgis</Parameter>
      <Parameter name="password"></Parameter>
      <Parameter name="host">localhost</Parameter>
      <Parameter name="port">5432</Parameter>
      <Parameter name="user">helmi</Parameter>
      <Parameter name="dbname">road</Parameter>
      <Parameter name="table">(select * no_jalan, 'lebuhraya' as jenis, the_geom from jalanraya.lebuhraya) as jalan</Parameter>
      <Parameter name="estimate_extent">false</Parameter>
      <Parameter name="extent">-180,-90,180,89.99</Parameter>
    </Datasource>
  </Layer>

My workaround (only tested on Ubuntu Jaunty) is cast the new column as varchar.

(select * no_jalan, 'lebuhraya'::varchar as jenis, the_geom from jalanraya.lebuhraya) as jalan

Mapnik is better than MapGuide when rendering road labels

OptimizeRenderingWithPostGIS