От: Rod Taylor
Тема: Re: Index oddity
Дата: ,
Msg-id: 1086814597.2539.92.camel@jester
(см: обсуждение, исходный текст)
Ответ на: Re: Index oddity  (ken)
Ответы: Re: Index oddity  (ken)
Список: pgsql-performance

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Index oddity  (ken, )
 Re: Index oddity  (Rod Taylor, )
  Re: Index oddity  (ken, )
   Re: Index oddity  (Rod Taylor, )
    Re: Index oddity  (ken, )
     Re: Index oddity  (Rod Taylor, )
      Re: Index oddity  (ken, )
       Re: Index oddity  (Christopher Kings-Lynne, )
        Re: Index oddity  (Rod Taylor, )
         Re: Index oddity  (Mark Kirkwood, )
          Re: Index oddity  ("Joshua D. Drake", )
     Re: Index oddity  (Tom Lane, )
      Re: Index oddity (still)  (ken, )
       Re: Index oddity (still)  (Tom Lane, )

On Wed, 2004-06-09 at 16:50, ken wrote:
> Thanks Rod,
>
> This setting has no effect however.  If I set statistics to 1000, or

Okay.. but you never did send EXPLAIN ANALYZE output. I want to know
what it is really finding.

> On Wed, 2004-06-09 at 13:12, Rod Taylor wrote:
> > It seems to believe that the number of rows returned for the >49.999
> > case will be 4 times the number for the >50 case. If that was true, then
> > the sequential scan would be correct.
> >
> > ALTER TABLE <table> ALTER COLUMN diagonalsize SET STATISTICS 1000;
> > ANALZYE <table>;
> >
> > Send back EXPLAIN ANALYZE output for the >49.999 case.
> >
> > > The query plan for diagonalSize > 50.000 is ...
> > >
> > > Index Scan using nrgfeature_xys_index on nrgfeature f
> > > (cost=0.00..17395.79 rows=4618 width=220)
> > >    Index Cond: ((upperrightx > 321264.236977215::double precision) AND
> > > (lowerleftx < 324046.799812083::double precision) AND (upperrighty >
> > > 123286.261898636::double precision) AND (lowerlefty <
> > > 124985.927450476::double precision) AND (diagonalsize > 50::double
> > > precision))
> > >
> > > ... while for diagonalSize > 49.999 is ...
> > >
> > >  Seq Scan on nrgfeature f  (cost=0.00..31954.70 rows=18732 width=220)
> > >    Filter: ((upperrightx > 321264.236977215::double precision) AND
> > > (lowerleftx < 324046.799812083::double precision) AND (upperrighty >
> > > 123286.261898636::double precision) AND (lowerlefty <
> > > 124985.927450476::double precision) AND (diagonalsize > 49.999::double
> > > precision))
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 9: the planner will ignore your desire to choose an index scan if your
> >       joining column's datatypes do not match
> >



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