Re: Faster distinct query? - Mailing list pgsql-general

From Michael Lewis
Subject Re: Faster distinct query?
Date
Msg-id CAHOFxGpAHwxiTGSmuDDr8_Nw4LHsKozxSY2aS7Mwg2F1CK6JAw@mail.gmail.com
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In response to Re: Faster distinct query?  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Faster distinct query?  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
On Wed, Sep 22, 2021 at 2:48 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
"David G. Johnston" <david.g.johnston@gmail.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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