Pgrouting- A Practical Guide

| Problem | Likely Cause | Solution | |--------|--------------|----------| | Path not found | Disconnected network | Check pgr_analyzeGraph() to identify orphaned nodes | | Negative cost error | reverse_cost negative or zero for directed edges | Set one-way roads with reverse_cost = -1 , others >0 | | Very slow queries | Missing indexes | Create indexes on source , target , and geometry | | Topology fails | Tolerance too large | Reduce tolerance; ensure geometries snap correctly |

This populates the source and target columns and creates a vertices_tmp table containing all nodes. PgRouting- A Practical Guide

ALTER TABLE roads ADD COLUMN x1 FLOAT, y1 FLOAT, x2 FLOAT, y2 FLOAT; UPDATE roads SET x1 = ST_X(ST_StartPoint(geom)), y1 = ST_Y(ST_StartPoint(geom)), x2 = ST_X(ST_EndPoint(geom)), y2 = ST_Y(ST_EndPoint(geom)); | Problem | Likely Cause | Solution |

To see your route in QGIS or a web map like Leaflet, you must join the routing results back to your geometry table: UPDATE roads SET x1 = ST_X(ST_StartPoint(geom))

brew install pgrouting