Re: Large files for relations

Thanks all for the feedback.  It was a nice idea and it *almost*
works, but it seems like we just can't drop segmented mode.  And the
automatic transition schemes I showed don't make much sense without
that goal.

What I'm hearing is that something simple like this might be more acceptable:

* initdb --rel-segsize (cf --wal-segsize), default unchanged
* pg_upgrade would convert if source and target don't match

I would probably also leave out those Windows file API changes, too.
--rel-segsize would simply refuse larger sizes until someone does the
work on that platform, to keep the initial proposal small.

I would probably leave the experimental copy_on_write() ideas out too,
for separate discussion in a separate proposal.