Serving multi-layer tiles from PostGIS

[superrache]

Declaring multiple PostGIS layer tables in the configuration file makes Martin to serve multiple tiles (one tile service by layer). It would be useful to be able to declare all the layers in a same tile service.

Actual config file:

...
postgres:
  ...
  auto_published: false
  tables:
    buildings:
      layer_id: buildings
      schema: public
      table: buildings
      srid: 3857
      geometry_column: geom
      id_column: ~
      minzoom: 14
      maxzoom: 14
      bounds: [ -180.0, -90.0, 180.0, 90.0 ]
      extent: 4096
      buffer: 64
      clip_geom: true
      geometry_type: POLYGON
      properties:
        area_id: int4
    boundaries:
      layer_id: boundaries
      schema: public
      table: boundaries
      srid: 3857
      geometry_column: geom
      id_column: ~
      minzoom: 2
      maxzoom: 14
      bounds: [ -180.0, -90.0, 180.0, 90.0 ]
      extent: 4096
      buffer: 64
      clip_geom: true
      geometry_type: LINESTRING
      properties:
        way_id: int4
        admin_level: integer
        maritime: string
        disputed: string

What is generated in the /catalog:

{
    "tiles": {
        "boundaries": {
            "content_type": "application/x-protobuf",
            "description": "public.boundaries.geom"
        },
        "buildings": {
            "content_type": "application/x-protobuf",
            "description": "public.buildings.geom"
        }
    }
}

And in the boundaries TileJSON, only one vector_layers:

{
    "tilejson": "3.0.0",
    "tiles": [
        "http://localhost:3000/boundaries/{z}/{x}/{y}"
    ],
    "vector_layers": [
        {
            "id": "boundaries",
            "fields": {
                "admin_level": "integer",
                "disputed": "string",
                "maritime": "string",
                "way_id": "int4"
            }
        }
    ],
    "bounds": [-180, -90, 180, 90],
    "description": "public.boundaries.geom",
    "maxzoom": 14,
    "minzoom": 2,
    "name": "boundaries"
}

It would be useful to declare a MVT service "all" containing both "boundaries" and "buildings" in vector_layers.

Maybe it's possible but didn't find how to do that in the documentation.

[CommanderStorm]

It would be useful to declare a MVT service "all" containing both "boundaries" and "buildings" in vector_layers.

Adding a special ID all to mean all layer_id's would be breaking for users that expect that ID to behave differntly in a somewhat sublte way.
=> adding that ID alias is likely not a good idea.

I think your usage is to have composite sources boundaries,buildings instead which serves them both.
relevant docs: https://maplibre.org/martin/sources-composite.html

Does this solve your issue?

[CommanderStorm]

Can the docs be improved?
Where did you look to find this? 🤔

[superrache]

Yes, composite sources do exactly what I want, I didn't seem clear to me the first time I read it in the doc.
If the full layer list is not already known, it can be revealed by /catalog then composed in a custom order.
I am looking for serving a layer scheme such as Shortbread that could have about 50 layers, so requests URL for TileJSON and tiles could be long. Maybe a feature to automatically aggregate all layers could be useful.

[CommanderStorm]

so Request-URL for TileJSON and tiles could be long

If this is a current problem instead of an usability issue for you (I don't think it is), you can solve it via using something like planetiler to generate a .mbtiles/.pmtiles container as one layer.
Depending on your usecase, this might have performance advantages (at the cost of potential freshness, depending on your setup)

There is also this issue for aliasing to subscribe to in the meantime:

• Add support for tile, sprite, and font source aliasing #1076