COPY FREEZE and setting PD_ALL_VISIBLE/visibility map bits

Hi,

Jeff Janes raised an issue [1] about PD_ALL_VISIBLE not being set correctly
while loading data via COPY FREEZE and had also posted a draft patch.

I now have what I think is a more complete patch. I took a slightly
different approach and instead of setting PD_ALL_VISIBLE bit initially and
then not clearing it during insertion, we now recheck the page for
all-frozen, all-visible tuples just before switching to a new page. This
allows us to then also mark set the visibility map bit, like we do in
vacuumlazy.c

Some special treatment is required to handle the last page before bulk
insert it shutdown. We could have chosen not to do anything special for the
last page and let it remain unfrozen, but I thought it makes sense to take
that extra effort so that we can completely freeze the table and set all VM
bits at the end of COPY FREEZE.

Let me know what you think.

Thanks,
Pavan

[1]
https://www.postgresql.org/message-id/CAMkU%3D1w3osJJ2FneELhhNRLxfZitDgp9FPHee08NT2FQFmz_pQ%40mail.gmail.com

--
Pavan Deolasee http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services