ST_GeogFromGeoJSON 在 bigquery 中失败而在 postgres 中成功

Question

We have geojson polygons we would like to convert to a geo object in bigquery using ST_GeogFromGeoJSON. The conversion fails in bigquery while is successful in postgres using the equivalent command ST_GeomFromGeoJSON.

I am familiar with the SAFE prefix that can be added to the the bigquery call, but we would like to use the object and not just ignore it in case the conversion fails. I tried converting the object using ST_CONVEXHULL but wasn't able to make it work.

Is there some work around in bigquery?

Example:

Running the following command in bigquery

select ST_GeogFromGeoJSON('{"type":"Polygon","coordinates":[[[-82.022982,26.69785],[-81.606813,26.710698],[-81.999574,26.109253],[-81.615053,26.105558],[-82.022982,26.69785]]]}')

returns

Query failed: ST_GeogFromGeoJSON failed: Invalid polygon loop: Edge 4 crosses edge 9

While runs successfully in postgres

select ST_GeomFromGeoJSON('{"type":"Polygon","coordinates":[[[-82.022982,26.69785],[-81.606813,26.710698],[-81.999574,26.109253],[-81.615053,26.105558],[-82.022982,26.69785]]]}')

Answer 1

October 2020 Update for this post

No more any tricks needed - ST_GEOGFROMGEOJSON and ST_GEOGFROMTEXT geographic functions now support a new make_valid parameter. If set to TRUE, the function attempts to correct polygon issues when importing geography data.

So, below simple statement works perfectly now...

select ST_GeogFromGeoJSON(
  '{"type":"Polygon","coordinates":[[[-0.49044,51.4737],[-0.4907,51.4737],[-0.49075,51.46989],[-0.48664,51.46987],[-0.48664,51.47341],[-0.48923,51.47336],[-0.48921,51.4737],[-0.49072,51.47462],[-0.49114,51.47446],[-0.49044,51.4737]]]}' 
  , make_valid => true
) 

and returns expected output

Answer 2

Below is for BigQuery Standard SQL

Query failed: ST_GeogFromGeoJSON failed: Invalid polygon loop: Edge 4 crosses edge 9
... Is there some work around in bigquery? ...

Proposed workaround is obviously naive and simple way of fixing specific issue while easily can be extended to more generic cases. The idea here is to extract coordinates and reorder them to eliminate the problem...

WITH test AS (
  SELECT '{"type":"Polygon","coordinates":[[[-82.022982,26.69785],[-81.606813,26.710698],[-81.999574,26.109253],[-81.615053,26.105558],[-82.022982,26.69785]]]}' AS geojson
)
SELECT ST_GEOGFROMGEOJSON('{"type":"Polygon","coordinates":' || fixed_coordinates || '}') AS geo
FROM (
  SELECT '[[[' || STRING_AGG(lat_lon, '],[') || '],[' || ANY_VALUE(ordered_coordinates[OFFSET(0)]) || ']]]' fixed_coordinates
  FROM (
    SELECT
      ARRAY( SELECT lon_lat
        FROM UNNEST(REGEXP_EXTRACT_ALL(JSON_EXTRACT(geojson, '$.coordinates'), r'\[+(.*?)\]+')) lon_lat
        ORDER BY CAST( SPLIT(lon_lat)[OFFSET(0)] AS FLOAT64), CAST(SPLIT(lon_lat)[OFFSET(1)] AS FLOAT64)
      ) ordered_coordinates
    FROM test
    ) t, t.ordered_coordinates lat_lon
)

This produces correct output

POLYGON((-82.022982 26.69785, -81.999574 26.109253, -81.8073135 26.1074055, -81.615053 26.105558, -81.606813 26.710698, -81.8148975 26.704274, -82.022982 26.69785))    

and respective visualization is

Answer 3

Below is for BigQuery Standard SQL

My previous answer is based on oversimplified logic of re-ordering coordinates. Obviously it will not work in more complex cases like below one

{‘type’:‘Polygon’,‘coordinates’:[[[-0.49044,51.4737],[-0.4907,51.4737],[-0.49075,51.46989],[-0.48664,51.46987],[-0.48664,51.47341],[-0.48923,51.47336],[-0.48921,51.4737],[-0.49072,51.47462],[-0.49114,51.47446],[-0.49044,51.4737]]]}

Is there some more advanced sorting logic that can be applied?

So more complex logic can be used to address this

#standardSQL
WITH test AS (
  SELECT '{"type":"Polygon","coordinates":[[[-0.49044,51.4737],[-0.4907,51.4737],[-0.49075,51.46989],[-0.48664,51.46987],[-0.48664,51.47341],[-0.48923,51.47336],[-0.48921,51.4737],[-0.49072,51.47462],[-0.49114,51.47446],[-0.49044,51.4737]]]}' geojson
), coordinates AS (
  SELECT CAST(SPLIT(lon_lat)[OFFSET(0)] AS FLOAT64) lon, CAST(SPLIT(lon_lat)[OFFSET(1)] AS FLOAT64) lat
  FROM test, UNNEST(REGEXP_EXTRACT_ALL(JSON_EXTRACT(geojson, '$.coordinates'), r'\[+(.*?)\]+')) lon_lat), stats AS (
  SELECT ST_CENTROID(ST_UNION_AGG(ST_GEOGPOINT(lon, lat))) centroid FROM coordinates
) 
SELECT ST_MAKEPOLYGON(ST_MAKELINE(ARRAY_AGG(point ORDER BY sequence))) AS polygon
FROM (
  SELECT point, 
    CASE 
      WHEN ST_X(point) > ST_X(centroid) AND ST_Y(point) > ST_Y(centroid) THEN 3.14 - angle
      WHEN ST_X(point) > ST_X(centroid) AND ST_Y(point) < ST_Y(centroid) THEN 3.14 + angle
      WHEN ST_X(point) < ST_X(centroid) AND ST_Y(point) < ST_Y(centroid) THEN 6.28 - angle
      ELSE angle
    END sequence
  FROM (
    SELECT point, centroid, 
      ACOS(ST_DISTANCE(centroid, anchor) / ST_DISTANCE(centroid, point)) angle
    FROM (
      SELECT centroid, 
        ST_GEOGPOINT(lon, lat) point, 
        ST_GEOGPOINT(lon, ST_Y(centroid)) anchor
      FROM coordinates, stats
    )
  )
) 

This approach produces correct output

POLYGON((-0.49075 51.46989, -0.48664 51.46987, -0.48664 51.47341, -0.48923 51.47336, -0.48921 51.4737, -0.49072 51.47462, -0.49114 51.47446, -0.49044 51.4737, -0.4907 51.4737, -0.49075 51.46989))

which is visualized as below