(1) One of my mentors--Alvaro Herrera--suggested me to have a look on the
UPSERT. It may be a good point to be able to achieve the same functionality
as during the ON CONFLICT DO NOTHING, when COPY actually inserts tuples
and errors handling is turned on. It could additionally reduce number of failed
subtransactions and reduce XIDs consumption, while still ignoring some common
errors like unique index violation.
Adding a full support of ON CONFLICT DO NOTHING/UPDATE to COPY seems
to be a large separated task and is out of the current project scope, but maybe there is
a relatively simple way to somehow perform internally tuples insert with
ON CONFLICT DO NOTHING? I have added Peter Geoghegan to cc, as
I understand he is the major contributor of UPSERT in PostgreSQL. It would be great
if he will answer this question.
