| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org> |
| Subject: | Re: Improvement of procArray.xmin for VACUUM |
| Date: | 2007-03-27 02:12:39 |
| Message-ID: | 200703270212.l2R2CdJ10077@momjian.us |
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| Lists: | pgsql-patches |
Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)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(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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