Re: Extremely slow intarray index creation and inserts.

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От Tom Lane
Тема Re: Extremely slow intarray index creation and inserts.
Дата
Msg-id 15055.1237407686@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: Extremely slow intarray index creation and inserts.  (Ron Mayer)
Ответы Re: Extremely slow intarray index creation and inserts.  (Oleg Bartunov)
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Extremely slow intarray index creation and inserts.  (Ron Mayer, )
 Re: Extremely slow intarray index creation and inserts.  (Ron Mayer, )
  Re: Extremely slow intarray index creation and inserts.  (Tom Lane, )
   Re: Extremely slow intarray index creation and inserts.  (Ron Mayer, )
    Re: Extremely slow intarray index creation and inserts.  (Tom Lane, )
     Re: Extremely slow intarray index creation and inserts.  (Oleg Bartunov, )
      Re: Extremely slow intarray index creation and inserts.  (Tom Lane, )
       Re: Extremely slow intarray index creation and inserts.  (Oleg Bartunov, )
        Re: Extremely slow intarray index creation and inserts.  (Oleg Bartunov, )
Ron Mayer <> writes:
> Oleg Bartunov wrote:
> OB:> it's not about short or long arrays, it's about small or big
> OB:> cardinality of the whole set (the number of unique elements)

> I'm re-reading the docs and still wasn't obvious to me.   A
> potential docs patch is attached below.

Done, though not in exactly those words.  I wonder though if we can
be less vague about it --- can we suggest a typical cutover point?
Like "use gist__intbig_ops if there are more than about 10,000 distinct
array values"?  Even a rough order of magnitude for where to worry
about this would save a lot of people time.

            regards, tom lane

Index: intarray.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/intarray.sgml,v
retrieving revision 1.5
retrieving revision 1.6
diff -c -r1.5 -r1.6
*** intarray.sgml    10 Dec 2007 05:32:51 -0000    1.5
--- intarray.sgml    18 Mar 2009 20:18:18 -0000    1.6
***************
*** 237,245 ****
    <para>
     Two GiST index operator classes are provided:
     <literal>gist__int_ops</> (used by default) is suitable for
!    small and medium-size arrays, while
     <literal>gist__intbig_ops</> uses a larger signature and is more
!    suitable for indexing large arrays.
    </para>

    <para>
--- 237,246 ----
    <para>
     Two GiST index operator classes are provided:
     <literal>gist__int_ops</> (used by default) is suitable for
!    small- to medium-size data sets, while
     <literal>gist__intbig_ops</> uses a larger signature and is more
!    suitable for indexing large data sets (i.e., columns containing
!    a large number of distinct array values).
    </para>

    <para>

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