# pgRouting Manual (2.1.0)

## Performance Tips

## For the Routing functions:

Note

To get faster results bound your queries to the area of interest of routing to have, for example, no more than one million rows.

## For the topology functions:

When “you know” that you are going to remove a set of edges from the edges table, and without those edges you are going to use a routing function you can do the following:

Analize the new topology based on the actual topology:

    pgr_analyzegraph('edge_table',rows_where:='id < 17');

Or create a new topology if the change is permanent:

    pgr_createTopology('edge_table',rows_where:='id < 17');
    pgr_analyzegraph('edge_table',rows_where:='id < 17');

Use an SQL that “removes” the edges in the routing function

    SELECT id, source, target from edge_table WHERE id < 17

When “you know” that the route will not go out of a particular area, to speed up the process you can use a more complex SQL query like

    SELECT id, source, target from edge_table WHERE
            id < 17 and
            the_geom  && (select st_buffer(the_geom,1) as myarea FROM  edge_table where id=5)

Note that the same condition `id < 17` is used in all cases.