PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Thom Brown <thom(at)linux(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
But surely it should be possible to use DO NOTHING without inferring some particular unique index? That's possible with an approach based on inheritance.