| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> |
| Cc: | Shaun Thomas <sthomas(at)townnews(dot)com>, Gunther Schadow <gunther(at)aurora(dot)regenstrief(dot)org>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Critical performance problems on large databases |
| Date: | 2002-04-11 17:56:16 |
| Message-ID: | 200204111756.g3BHuGL13708@candle.pha.pa.us |
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| Lists: | pgsql-general |
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.
We do have this TODO item:
* Allow ORDER BY ... LIMIT to select top values without sort or index
using a sequential scan for highest/lowest values
--
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
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