SELECT util.search_path_append('util');

-- runtime: 0.3 s ("Time: 256.926 ms") @starscream

SELECT set_col_types(:table_str, ARRAY[

  ('minDBHcm', 'double precision')

, ('maxDBHcm', 'double precision')

]::col_cast[]);

SELECT mk_derived_col((:table_str, 'diameterBreastHeight_cm'), $$_avg("minDBHcm", "maxDBHcm")$$); -- runtime: 0.4 s ("Time: 431.405 ms") @starscream