Re: cpu_tuple_cost

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От Gregory Stark
Тема Re: cpu_tuple_cost
Дата
Msg-id 87psy1mq66.fsf@stark.xeocode.com
обсуждение исходный текст
Ответ на cpu_tuple_cost  (Daniel Schuchardt <daniel_schuchardt@web.de>)
Ответы Re: cpu_tuple_cost  (David Brown <time@bigpond.net.au>)
Список pgsql-performance
Bruce Momjian <pgman@candle.pha.pa.us> wrote:

> Agreed.  I think we should reduce it at least to 3.

Note that changing it from 4 to 3 or even 2 is unlikely to really change much.
Many of the plans people complain about turn out to have critical points
closer to 1.2 or 1.1.

The only reason things work out better with such low values is because people
have data sets that fit more or less entirely in RAM. So values close to 1 or
even equal to 1 actually represent the reality.

The "this day and age" argument isn't very convincing. Hard drive capacity
growth has far outstripped hard drive seek time and bandwidth improvements.
Random access has more penalty than ever.

--
greg

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