Displaying Columns added with views_query_alter

Thanks! Will do.

/r/b

Just to provide some background. I am doing a "spatial join" which means that I am using two geometry columns (a point and a polygon) to determine if two separate nodes intersect in the same space. My system is based on postgreSQL, so I use the postgis extension to SQL to accomplish the intersection. I have the geometries stored in separate tables. My code is all done in a custom module as below.

My tables:
1. 'node' - My base table
2. 'data_node_point' - a table with a NID that refers and has a point geometry (basically a latitude and longitude)
3. 'data_node_coverage' - A table with an entity_id (also a nid reference) and a multi-polygon geometry (a 2 dimensional spatial area)
4. Both 'data_node_point' and 'data_node_coverage' have a dummy column 'status' which is always 1 in order to provide an initial join condition because it seems that the 'join' requires something non-null there (maybe I am wrong, but no harm occurs I suppose).

My code outline steps are as follows:
1. I join the point table 'data_node_point' to 'node' via matching 'nid' columns - I use the function "$query->addRelationship" to enable me to join to the table 'data_node_point' later.
2. I add columns from 'data_node_point' - 'nid' and 'the_geom'
3. I join the table 'data_node_coverage' to 'data_node_point' via a spatial containment operator - if the lat/lon in 'data_node_point' lies inside of the boundaries of 'data_node_coverage' then I include it.
4. I screen for null geometries which would indicate that the original node has no entry in the point table or no overlapping coverage.

function wsp_devel_views_query_alter(&$view, &$query) {

   if ($view->name=="wsp_coverage_systems") {
      error_log("Found wsp_coverage_systems");

      $join = new views_join;
      $join->construct('data_node_point','node', 'nid', 'nid');
      $res = $query->add_relationship('data_node_point', $join, 'data_node_point', 'node');
      $res = $query->add_field('data_node_point', 'nid');
      $res = $query->add_field('data_node_point', 'the_geom');
      
      $join = new views_join;
      $geojoin = 'data_node_coverage.the_geom && data_node_point.the_geom';
      $geojoin .= ' AND contains(data_node_coverage.the_geom, data_node_point.the_geom )';
      $join->construct('data_node_coverage', 'data_node_point','status', 'status', $geojoin);
      $res = $query->add_table('data_node_coverage', 'data_node_point', $join, 'data_node_coverage');
      $res = $query->add_field('data_node_coverage', 'entity_id');
      $res = $query->add_field('data_node_coverage', 'the_geom');
      
      if (isset($view->args[0])) {
         $query->add_where_expression(0, 'data_node_coverage.entity_id = ' . $view->args[0]);
      }
      $query->add_where_expression(0, 'data_node_point.the_geom is not null');
      $query->add_where_expression(0, 'data_node_point.the_geom is not null');
   }
   
}