Re: [HACKERS] Solution for LIMIT cost estimation

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От Hannu Krosing
Тема Re: [HACKERS] Solution for LIMIT cost estimation
Дата
Msg-id 38A8A141.DDDE8548@tm.ee
обсуждение исходный текст
Ответ на Solution for LIMIT cost estimation  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: [HACKERS] Solution for LIMIT cost estimation  (Don Baccus <dhogaza@pacifier.com>)
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Don Baccus wrote:
> 
> At 11:41 AM 2/14/00 +0200, Hannu Krosing wrote:>Maybe we should still discourage the use of LIMIT, and rather
introduce
> >another "mode" for optimiser, activated by SET FastStart TO 'ON'.
> >Then queries with limit could be rewritten into
> >SET FastStart to 'ON';
> >DECLARE
> >MOVE
> >FETCH
> >CLOSE
> >SET FastStart to PREVIOUS_VALUE;
> >
> >also maybe we will need PUSH/POP for set commands ?
> 
> Well...personally I don't see LIMIT as being particularly harmful,
> and it is a convenience.  Remember, for the web space you're speaking
> of keeping overhead low is a real concern, and requiring a series
> of queries where currently only one needed will probably go over like
> a lead ballon.

I meant that the _backend_ could (in some distant future, when the 
optimiser is perfect :) implement LIMIT as above sequence.

---------------
Hannu


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