Re: concerns around pg_lsn

On the topic of pg_lsn, I recently noticed that there's no
operator(+)(pg_lsn,bigint) nor is there an operator(-)(pg_lsn,bigint) so
you can't compute offsets easily. We don't have a cast between pg_lsn and
bigint because we don't expose an unsigned bigint type in SQL, so you can't
work around it that way.

I may be missing the obvious, but I suggest (and will follow with a patch
for) adding + and - operators for computing offsets. I was considering an
age() function for it too, but I think it's best to force the user to be
clear about what current LSN they want to compare with so I'll skip that.

-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 2ndQuadrant - PostgreSQL Solutions for the Enterprise