layer:
  id: "waterway"
  description: |
      Rivers based of OpenStreetMap [waterways](http://wiki.openstreetmap.org/wiki/Waterways) for *z9* to *z14*
      and Natural Earth rivers and lake centerlines from *z3* to *z8*.
      Linestrings without a name or which are too short are filtered
      out at low zoom levels. Waterways do no not have a `subclass` field.
  buffer_size: 4
  fields:
    name: |
        The OSM [`name`](http://wiki.openstreetmap.org/wiki/Key:name) value of the waterway.
        The `name` field is empty for NaturalEarth data until **z9** when OSM data is used.
    class: |
        The original value of the [`waterway`](http://wiki.openstreetmap.org/wiki/Key:waterway) tag.
        Can be one of [`stream`](http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dstream),
        [`river`](http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver),
        [`canal`](http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dcanal),
        [`drain`](http://wiki.openstreetmap.org/wiki/Tag:waterway%3Ddrain),
        [`ditch`](http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dditch)`.
  datasource:
    geometry_field: geometry
    query: (SELECT geometry, name, class FROM layer_waterway(!bbox!, z(!scale_denominator!))) AS t
schema:
  - ./merge_waterway.sql
  - ./waterway.sql
datasources:
  - type: imposm3
    mapping_file: ./mapping.yaml