Graph creation functions

[tomkom]

-- Preamble: Just stumbled upon the extension, very excited, thank you!

Functionality suggestion ( maybe already in pipeline):

Explicit graph data are not that common and often have to be created by recomputing the topology. This is common in the spatial context ( street lanes), where graphs are computed by analyzing topological relationships between member geometries.

The result is a data structure -- the edge table. See for example the behaviour of [pg_routing] (https://docs.pgrouting.org/latest/en/pgr_createTopology.html), potentially with an additional vertices table.

It would be awesome if it was possible to create the input structures in DUCK/PGQ, instead of having to craft them separately.

[Dtenwolde]

Hi Tom,

Thank you :) I'll start working more on the extension again in the near future (wrapping up an internship right now)

I am new to pg_routing, so just for my understanding, what would be the input to pgr_createTopology? Would that be an already existing edge_table (or a csv file with a source and target column?) through which the edge_table gets updated/created according to the rows_where parameter and the creation of a vertex_table?

If so, that sounds like a feature I would definitely like to add to the list, seems quite useful and improves usability :) Please let me know!

[tomkom]

Yes, an edge table that contains a geom column. Think of it as generating a graph def from a vector drawing. These are typically linestring edges (note, we distinguish vertices of a linestring, an graph nodes, where 2+ linestrings intersect). Duckdb implements spatial geometries as here https://duckdb.org/docs/extensions/spatial.html

Tolerance is for "snapping" linestrings if there is a small gap between end vertices.

[Dtenwolde]

I see, I believe there are opportunities to combine the spatial and duckpgq extension, so I'll keep this in mind. Thank you :)

[tomkom]

JUst catching up on this, did anyone manage to experiment with graph creation based on the DuckDB geometry support? This is now beautifully mainstream, and supporting graph based analytics ( shortest path) requires the ability to create a network from the geometries from a table that contains "lines". Is this something that is now tackled in the duckpg extension development?

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.