-- casts should cast from istore to bigistore;
SELECT '1=>1, -1=>-1'::istore::bigistore;
      bigistore       
----------------------
 "-1"=>"-1", "1"=>"1"
(1 row)

-- casts should cast from bigistore to istore;
SELECT '1=>1, -1=>-1'::bigistore::istore;
        istore        
----------------------
 "-1"=>"-1", "1"=>"1"
(1 row)

-- casts should fail cast from bigistore to istore if any value is to big;
SELECT '1=>1, -1=>3000000000'::bigistore::istore;
ERROR:  integer out of range