Re: Improvement of procArray.xmin for VACUUM

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 ...

            regards, tom lane