Nearest Feature (KNN / <->)

Use this skill when you need the nearest feature to a point/geometry (e.g., nearest feeder, nearest segment, nearest hub).

PostGIS supports fast nearest-neighbor searches using the KNN operator <-> when a GiST index exists.

When to use

• “Find the nearest X to this point”
• “Rank candidates by proximity”
• “Pick the closest feature per input row”

Core rules

• KNN <-> works best with GiST indexes on geometry columns
• <-> orders by distance in the geometry’s coordinate system (SRID units)
• For meaningful distances, use a projected SRID or geography (meters)
• Keep queries index-friendly: avoid wrapping the indexed column in transforms inside ORDER BY when possible