| From: | Michael Lewis <mlewis(at)entrata(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Israel Brewster <ijbrewster(at)alaska(dot)edu>, PostgreSQL Mailing Lists <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Faster distinct query? |
| Date: | 2021-09-22 22:51:51 |
| Message-ID: | CAHOFxGpAHwxiTGSmuDDr8_Nw4LHsKozxSY2aS7Mwg2F1CK6JAw@mail.gmail.com |
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| Lists: | pgsql-general |
On Wed, Sep 22, 2021 at 2:48 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > There is no where clause so I'm doubtful there is much to be gained going
> > down this path. The Index-Only scan seems like an optimal way to obtain
> > this data and the existing query already does that.
>
> The "index-only" scan is reported to do 86m heap fetches along the
> way to returning 812m rows, so the data is apparently pretty dirty.
>
Do you say that because you would expect many more than 10 tuples per page?
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