| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Hadi Moshayedi <hadi(at)citusdata(dot)com>, Postgres General <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: index-only-scan when there is an index on all columns |
| Date: | 2018-02-27 22:10:20 |
| Message-ID: | CAKFQuwbs8rfMk4TodXU_YzaW7BR1krY+ttATqJge2nS-jtTUEg@mail.gmail.com |
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| Lists: | pgsql-general |
On Tue, Feb 27, 2018 at 2:58 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:
>
> > Also, I recall discussion that select statements will touch the
> visibility
> > map (hence causing write I/O even in a read-only query) but [1] indicates
> > that only vacuum will set them ddl will clear them.
>
> Hm, I don't recall that, but I've not been involved in the last few rounds
> of hacking on that mechanism.
>
I was confusing hint bits with the visibility map, sorry for the noise
and/or confusion.
David J.
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