Improvement: add "prev" column to pgr_dijkstraVia result set

[claudiadragoste]

Problem

Currently, pgr_dijkstraVia returns the following fields:

seq | path_id | path_seq | start_vid | end_vid | node | edge | cost | agg_cost | route_agg_cost

However, unlike other pgRouting functions such as pgr_drivingDistance, it does not expose predecessor information.

Improvement

Add prev column to the result set of pgr_dijkstraVia.
Proposed output:

seq | path_id | path_seq | start_vid | end_vid | prev | node | edge | cost | agg_cost | route_agg_cost

Where: prev = previous node
Alternatives

[AdityaRanaX]

Hi, I'd like to take a shot at this if it's still open.

I looked into how pgRouting has handled similar column additions in the past to figure out the right approach here. pgr_dijkstraVia is currently listed as Proposed, not Official, and I found precedent for direct signature changes on functions at that stage rather than new overloads — pgr_dijkstra had columns added directly to its existing signatures while stabilizing (e.g. start_vid/end_vid added to the One-to-Many and Many-to-One variants), and pgRouting 3.7 added a pred column directly to pgr_drivingDistance's existing output, documented as a breaking change in the release notes. That looks like the closest precedent to what's being asked here.

Based on that, I went with adding prev directly to the existing pgr_dijkstraVia signature rather than introducing a new overload, documented as a breaking change in the next release notes.

For context on where I'm coming from: I've been working through the pgRouting workshop hands-on (built network views from real OSM data, ran pgr_connectedComponents and related functions against it), and I've since cloned and built the main pgrouting repo from source, so I have a working dev environment to test changes against.

Opened #3149 with this approach — happy to adjust based on feedback.