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JSON Config Syntax

This syntax is used by the HOT Export Tool, and it's FastAPI backend, Raw Data API. The YAML format was considered to be too simple for complex queries, so this JSON format was created to replace it. This is identical the the format used by those tools.

Geometry

This is a GeoJson geometry that defines the project boundary. Since the datbase is huge, this limits the area the query is performed in.

Filters

The filters do the real work of this format. The tags keyword is followed by the desired geometry, which determine which database tables get searched. If all_geometry is supplied, then all the tables are queried. It can also be centroid, which then returns onl points.

The syntax is the same for the join_or keyword, or the join_and keyword. It's a list of keyword/value pairs. If it's an empty list, this is the equivalant of using IS NOT NULL in SQL. If it has a value instead, then only features with that value are returned.

Centroid

This is true or false on whether the result should only be centroids of all the geometries. The default is false if this is not present.

Example

Unlike the YAML format that generates an SQL query, the raw data API wants this JSON file. This can be generated however from the YAML config file. If used as a config file, an identical version is generated from the parsed config data. This way it can be used for both input and output.

This config file is for highway extracts.

{
 "geometry": {
  "type": "Polygon",
  "coordinates": [
   [
    [
     [
      -105.390892,
      39.743926
     ],
     # More coordinates remove
    ]
   ]
  ]
 },
 "filters": {
  "tags": {
   "all_geometry": {
    "join_or": {
     "highway": [],
     "waterway": []
    },
    "join_and": {
     "bridge": []
    }
   }
  }
 },
}

Last update: July 10, 2024