layer:
  id: "boundary"
  description: |
      Contains administrative boundaries as linestrings.
      Until z4 [Natural Earth data](http://www.naturalearthdata.com/downloads/) is used after which
      OSM boundaries ([`boundary=administrative`](http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative))
      are present from z5 to z14 (also for maritime boundaries with admin_level <= 2 at z4).
      OSM data contains several [`admin_level`](http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative#admin_level)
      but for most styles it makes sense to just style `admin_level=2` and `admin_level=4`.
  fields:
    admin_level: |
        OSM [admin_level](http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative#admin_level)
        indicating the level of importance of this boundary.
        The `admin_level` corresponds to the lowest `admin_level`
        the line participates in.
        At low zoom levels the Natural Earth boundaries are mapped to the equivalent admin levels.
    disputed:
      description: |
          Mark with `1` if the border is disputed.
      values: [0, 1]
    maritime:
      description: |
          Mark with `1` if it is a maritime border.
      values: [0, 1]
  buffer_size: 4
  datasource:
    geometry_field: geometry
    query: (SELECT geometry, admin_level, disputed, maritime FROM layer_boundary(!bbox!, z(!scale_denominator!))) AS t
schema:
  - ./boundary.sql