Re: Synchronized scans - Mailing list pgsql-patches

From Jeff Davis
Subject Re: Synchronized scans
Date
Msg-id 1181338674.7660.215.camel@dogma.v10.wvs
Whole thread Raw
In response to Re: Synchronized scans  (Jeff Davis <pgsql@j-davis.com>)
Responses Re: Synchronized scans  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-patches
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@enterprisedb.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


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