The edges query

Every routing function takes its graph as a string of SQL. duckrouting runs that query and reads four required columns plus one optional one.

Required columns

Column	Type	Meaning
id	BIGINT	Identifier reported back in the edge output column
source	BIGINT	Start vertex
target	BIGINT	End vertex
cost	DOUBLE	Weight of traversing source → target

Optional column

Column	Type	Meaning
reverse_cost	DOUBLE	Weight of traversing target → source

Column names are matched case-insensitively, and any numeric type is accepted and cast. Missing required columns raise a binder error; a NULL in id, source, target or cost raises an input error.

How costs encode direction

This is the part that surprises people, and it is pgRouting's convention:

• A negative cost means the edge does not exist in that direction. It is not a cheap edge, and it is not an error.
• A missing or NULL reverse_cost is treated exactly as -1.

So with cost = -1, reverse_cost = 1 the edge is traversable only from target to source. Omit reverse_cost entirely and every edge becomes strictly one-way.

In an undirected query (directed => false) both values still apply, but direction stops mattering: the edge is usable from either end as long as at least one of the two costs is non-negative.

Infinite costs

cost = 'Infinity' marks an edge as usable but unboundedly expensive. Routes that must cross it are returned with agg_cost of Infinity, matching pgRouting. Internally the value is stored as a large finite sentinel, because Boost will not relax an edge whose weight is a true infinity. Note that -Infinity is also treated as that sentinel rather than as "no edge" -- again matching pgRouting, which tests for infinity before it tests for a negative cost.

Example

A one-way street network where cost is travel time and closures are excluded before routing:

SELECT * FROM duckrouting_dijkstra(
  $$
  SELECT id, source, target,
         CASE WHEN oneway THEN travel_time ELSE travel_time END AS cost,
         CASE WHEN oneway THEN -1          ELSE travel_time END AS reverse_cost
  FROM streets
  WHERE NOT closed
  $$,
  100, 250);

Using a dollar-quoted string keeps the inner SQL readable and avoids escaping single quotes.