Finding points along a path

You should be able to run a SQL statement using the PostGIS function ST_LineLocatePoint to select the relative distance along the route. You will need a single route, a filter for the max distance from the route, and an order by clause.

This is untested, but should get you started:

Select    points.pointID
from      points, 
          rountes 
where     rountes.routeID = :routeid 
  and     ST_Intersects(points.pointShape, ST_Buffer(route.rounteShape, 50000))
order by  ST_LineLocatePoint(route.rounteShape, points.pointShape); 

You could filter by ST_Distance(points.pointShape, route.routeShape) <= 50000, but I'm not sure if that is going to use the spatial index.

---

You need two postgis functions ST_Buffer and ST_Line_Locate_Point.