Postgis remove all rings from all polygons

remove_rings.sql

UPDATE multipoly_table_with_rings AS myrings
SET geom = noring.geom
FROM (
    SELECT id, ST_Collect(ST_MakePolygon(geom)) AS geom
    FROM (
        SELECT id, ST_NRings(geom) AS nrings, 
            ST_ExteriorRing((ST_Dump(geom)).geom) AS geom
        FROM multipoly_table_with_rings
        WHERE ST_NRings(geom) > 1
        ) AS foo
    GROUP BY gid, nrings
    HAVING nrings > COUNT(id)
    ) AS noring
WHERE myrings.id = noring.id;