Re: Synchronized scans - Mailing list pgsql-patches

From Jeff Davis
Subject Re: Synchronized scans
Date
Msg-id 1181329029.7660.201.camel@dogma.v10.wvs
Whole thread Raw
In response to Re: Synchronized scans  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Synchronized scans  (Jeff Davis <pgsql@j-davis.com>)
List pgsql-patches
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
make a change like that before 8.3 though, right?

> This would be a trivial addition to the code-as-committed (clear
> rs_syncscan upon backing up by a page) but I didn't add it.  Any
> strong feelings one way or the other?  AFAIK the only case where
> it'd happen is if someone reads forwards in a large-seqscan cursor
> for awhile and then reads backwards.  You could argue that doing
> that is a good reason to drop them out of the syncscan pack ...
>

I don't feel strongly about it at all. Mostly because it seems so rare
that it would matter.

Regards,
    Jeff Davis


pgsql-patches by date:

Previous
From: Tom Lane
Date:
Subject: Re: Synchronized scans
Next
From: Jeff Davis
Date:
Subject: Re: Synchronized scans