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CREATE OR REPLACE FUNCTION LineStringFromPoints(linejsonb JSONB)
  RETURNS geometry AS
$BODY$
DECLARE
  p      geometry;
  i      RECORD;
  srid   INTEGER = 4326;
  points GEOMETRY [];
  str    TEXT;
BEGIN

  FOR i IN SELECT
             cast(t ->> 'lng' AS FLOAT) AS lng,
             cast(t ->> 'lat' AS FLOAT) AS lat
           FROM jsonb_array_elements(linejsonb) t
  LOOP
    points = points || st_makepoint(i.lng, i.lat);
  END LOOP;
  RETURN st_makeline(points);
END;
$BODY$
LANGUAGE PLPGSQL;