Re: Synchronized scans

On Fri, 2007-06-08 at 11:57 -0700, Jeff Davis wrote:
> On Fri, 2007-06-08 at 14:36 -0400, Tom Lane wrote:
> > Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> > > Here's an update of the patch. I reverted the behavior at end of scan
> > > back to the way it was in Jeff's original patch, and disabled reporting
> > > the position when moving backwards.
> >
> > Applied with minor editorializations --- notably, I got rid of the
> > HeapScanDesc dependency in syncscan.c's API, so that it could be used
> > in other contexts (VACUUM, anyone?). There were a few glitches in the
> > heapam.c code too.
>
> I think VACUUM would be an ideal place for it. I assume we don't want to

I have a few thoughts:

* For a large table, do lazy_scan_heap, scan_heap, and a sequential
scan usually progress at approximately the same rate?

* Are there any other parts of the vacuum process that may benefit?

* Just adding in the syncscan to scan_heap and lazy_scan_heap seems
very easy at first thought. Are there any complications that I'm
missing?

Regards,
Jeff Davis