[Mapserver-users] unclear on the concept

[Joel Gwynn]

Perhaps I'm going about this the wrong way.  I'm using perl mapscript, 
and I've got a postgis points layer and I want to get some points, say 
within a certain radius of Boston:

my $map = new mapscript::mapObj("$map_path/world_cities.map");
my $boston = new mapscript::pointObj(-71.1029968261719, 42.375);
my $city_layer = $map->getLayer(1);

if(my $r = $city_layer->queryByPoint($map, $boston, 
$mapscript::MS_MULTIPLE,10)){
    print "no results.\n";
}else{
    my $i = 0;
    print "status: $r\n";
    while(my $rc = $city_layer->getResult($i)){
    my $si = $rc->{shapeindex};
    print "shapeindex: $si\n";
    $i++;
    }
}

This prints out a bunch of shapeindex numbers.  What are those numbers? 
They don't seem to show up in my cities table in the database.  Can I 
use the mapscript object to access the points?