Turning a single MultiPolygon into many small polygons?
As OP figured out, the ST_Dump function from PostGIS is one way to explode multipart geometries to single ones:
When the input geometry is a collection or multi it will return a record for each of the collection components, ... .
ST_Dump is useful for expanding geometries. ... . For example it can be use to expand MULTIPOLYGONS into POLYGONS.
SELECT sometable.field1,
(ST_Dump(sometable.the_geom)).geom AS the_geom
FROM sometable;
The following is a related post with Python alternatives: Converting huge multipolygon to polygons