gistfile1.sql

### this works
SELECT cartodb_id, ST_GeomFromText(replace(replace(replace(replace(replace(geometry, '<Polygon><outerBoundaryIs><LinearRing><coordinates>', 'Linestring('), '</coordinates></LinearRing></outerBoundaryIs></Polygon>', ')'), ',', '$'), ' ', ','), '$', ' '),4326) geom  FROM test_yield_county

### the official query
delete FROM test_yield_county where geometry = '' 

with f as (SELECT cartodb_id, ST_GeomFromText(replace(replace(replace(replace(replace(geometry, '<Polygon><outerBoundaryIs><LinearRing><coordinates>', 'Linestring('), '</coordinates></LinearRing></outerBoundaryIs></Polygon>', ')'), ',', '$'), ' ', ','), '$', ' '),4326) geom  FROM test_yield_county order by geometry desc)

update test_yield_county d 
set the_geom = (
    SELECT ST_MakePolygon(ST_AddPoint(f.geom, ST_StartPoint(f.geom))) from f WHERE cartodb_id = d.cartodb_id LIMIT 1
)