pgr_drivingDistance uses the cost value you provide, and in the units you implicitly specify, meaning that when you add a column <traveling_time> (note that I use seconds in my example) as the time needed to traverse an edge (given the length and speed limit) and select that as cost, the functions result will represent the … Read more
You are building the point and the polygon – instead of having proper geometry column – which is inefficient. You haven’t talked about spatial index, so the intersect operation will be slow. You haven’t specified the complexity of the polygons: if they have many many vertices, an intersect operation will be slow. This can be … Read more
As stated in the linked post MakeValid is a database function, which means that it can be executed only during querying the database. It is 1-to-1 similar to the PostGIS usage of ST_MakeValid which cannot be executed outside of a table query (cannot exist autonomously). When you create the np object, and then you try … Read more