| From: | Atri Sharma <atri(dot)jiit(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Risk Estimation WAS: Planner hints in Postgresql |
| Date: | 2014-03-20 15:30:49 |
| Message-ID: | CAOeZVifc88H512xq31Dj3ccsn1ecArr8hStK8ZT-qbt92eJB9g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Mar 20, 2014 at 8:51 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Atri Sharma <atri(dot)jiit(at)gmail(dot)com> writes:
> > Now, why cannot we take the estimate of all the buckets behind the bucket
> > in which our value is present? Will that estimate not give us the
> fraction
> > of tuples that are expected to be before the first matching row?
>
> Uh, no, not unless you assume that the table happens to be perfectly
> sorted by the column's value.
>
>
>
Yes, that is true. So, if an attribute has an index present, can we do this
somehow?
Regards,
Atri
--
Regards,
Atri
*l'apprenant*
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