Re: Tsearch2 Initial Search Speed

От: Matthew Wakeling
Тема: Re: Tsearch2 Initial Search Speed
Дата: ,
Msg-id: Pine.LNX.4.64.0806171228480.3987@aragorn.flymine.org
(см: обсуждение, исходный текст)
Ответ на: Re: Tsearch2 Initial Search Speed  (Howard Cole)
Ответы: Re: Tsearch2 Initial Search Speed  (Howard Cole)
Список: pgsql-performance

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Tsearch2 Initial Search Speed  (Howard Cole, )
 Re: Tsearch2 Initial Search Speed  (Alan Hodgson, )
  Re: Tsearch2 Initial Search Speed  (Howard Cole, )
   Re: Tsearch2 Initial Search Speed  (Howard Cole, )
    Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
     Re: Tsearch2 Initial Search Speed  (Howard Cole, )
      Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
       Re: Tsearch2 Initial Search Speed  (Howard Cole, )
        Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
         Re: Tsearch2 Initial Search Speed  (Howard Cole, )
         Re: Tsearch2 Initial Search Speed  (Howard Cole, )
          Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
           Re: Tsearch2 Initial Search Speed  (Howard Cole, )
      Re: Tsearch2 Initial Search Speed  (Alan Hodgson, )
       Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
    Re: Tsearch2 Initial Search Speed  (Alan Hodgson, )
   Re: Tsearch2 Initial Search Speed  (Matthew Wakeling, )
 Re: Tsearch2 Initial Search Speed  (Howard Cole, )

On Tue, 17 Jun 2008, Howard Cole wrote:
> They both appear to do a scan on the email table (Why?).

The indexes don't contain copies of the row data. They only contain
pointers to the rows in the table. So once the index has been consulted,
Postgres still needs to look at the table to fetch the actual rows. Of
course, it only needs to bother looking where the index points, and that
is the benefit of an index.

Matthew

--
I've run DOOM more in the last few days than I have the last few
months.  I just love debugging ;-)  -- Linus Torvalds


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