Re: Improvement of procArray.xmin for VACUUM

Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Gregory Stark wrote:
> >> I have a question about what would happen for a transaction running a command
> >> like COPY FROM. Is it possible it would manage to arrange to have no live
> >> snapshots at all? So it would have no impact on concurrent VACUUMs? What about
> >> something running a large pg_restore?
>
> > Interesting idea.
>
> Indeed.  Currently, COPY forcibly sets a snapshot on the off chance
> something will use it, but I could certainly see making that happen
> "lazily", ie not at all in the simple case.
>
> pg_restore is probably a lost cause, at least if you are running it
> in single-transaction mode.  I guess there'd be tradeoffs as to whether
> to do that or not ...

The bottom line is that more optimizations for VACUUM dead tuple
identification are possible.

--
  Bruce Momjian  <bruce@momjian.us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +