Re: Critical performance problems on large databases

Oleg, I have added your name to this TODO list:

* Allow ORDER BY ... LIMIT to select top values without sort or index
using a sequential scan for highest/lowest values (Oleg)

---------------------------------------------------------------------------

Oleg Bartunov wrote:
> On Thu, 11 Apr 2002, Bruce Momjian wrote:
>
> > Gunther Schadow wrote:
> > > Oleg Bartunov wrote:
> > >
> > > > The big issue with LIMIT,OFFSET is that it still use all rows
> > > > for sorting. I already suggested to use partial sorting to avoid
> > > > sorting all rows if one selected only first 20 row, for example.
> > > > It's very important for Web applications because web users usually
> > > > read first 1-2 pages. Our experimnets have shown 6 times performance
> > > > win when using partial sorting.
> > >
> > >
> > > That is interesting. I haven't even dared to ask for this.
> > > Did you contribute that partial sorting code to postgresql?
> >
> >
> > We have the TODO item, but the code is not written yet.
> >
>
> Actually, we have libpsort for partial sorting and very crude patch for 7.1
> Jan and Tom were not optimist about that patch, so we need one bright
> person who could incorporate the idea of partial sorting and current sources
> and satisfy core developers. We have no time, unfortunately
>
>
> >
>
> Regards,
> Oleg
> _____________________________________________________________
> Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> Sternberg Astronomical Institute, Moscow University (Russia)
> Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
> phone: +007(095)939-16-83, +007(095)939-23-83
>
>

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026