Re: Synchronized scans

Heikki Linnakangas <heikki@enterprisedb.com> writes:
> For the record, this patch has a small negative impact on scans like
> "SELECT * FROM foo LIMIT 1000". If such a scan is run repeatedly, in CVS
> HEAD the first 1000 rows will stay in buffer cache, but with the patch
> each scan will start from roughly where previous one stopped, requiring
> more pages to be read from disk each time. I don't think it's something
> to worry about in practice, but I thought I'd mention it.

Urgh.  The answers change depending on (more or less) the phase of the
moon?  I've got a serious problem with that.  You might look back to
1997 when GEQO very nearly got tossed out entirely because it destroyed
reproducibility of query results.

            regards, tom lane