select pg_attribute.attname, pg_attribute.atttypid::int, pg_attribute.attnotnull,
pg_attribute.attlen, pg_attribute.atttypmod
from pg_class, pg_attribute
left join pg_attrdef on (pg_attrdef.adrelid = pg_attribute.attrelid and pg_attrdef.adnum =pg_attribute.attnum)
where lower(pg_class.relname) = '%s'
and pg_attribute.attnum > 0
and pg_attribute.attrelid = pg_class.oid
and pg_attribute.attisdropped = false
order by pg_attribute.attnum;

Вместо %s поставь имя своей таблицы и выполни запрос.