Re: How Postgresql Compares For Query And Load Operations

> On Saturday 14 July 2001 02:49, Tom Lane wrote:
>
> > >
> > > It would seem that Oracle's execution plan is more optimal.
> >
> > Hmm, since I don't know the details of Oracle's plan displays, it's hard
> > to comment on that --- but it looks to me like the plans are essentially
> > the same, with the small difference that Postgres chooses to use the
> > index on dim0 to filter ....(snipped )
>
> After a little thinking, I am inclined to agree with you Tom... I wondered if
> the difference might to be due to pure sequential scan performance
> differences. I tried this query :
>
> SELECT sum(val) FROM fact0
>
> for Postgres, Db2 and Oracle. The results were
>
> Postgres    2m25s
> Db2        40s
> Oracle        50s
>
> This seems to be the likely culprit. I suspect that the "many block/page read
> at once" type optimzations (prefetch for Db2 and mutli block read for Oracle)
> mean that table sequential scans are faster for these guys than Postgres.
>
> Thus on the bright side their access plans are not necessarily any better
> than Postgres !

Can you remind me about the OS you are using?

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