Re: release notes: tids & self-joins

On Thu, Jun 13, 2019 at 01:22:16PM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > The release notes say:
> >       <listitem>
> > <!--
> > Author: Tom Lane <tgl@sss.pgh.pa.us>
> > 2018-12-30 [b5415e3c2] Support parameterized TidPaths.
> > Author: Tom Lane <tgl@sss.pgh.pa.us>
> > 2018-12-30 [0a6ea4001] Add a hash opclass for type "tid".
> > -->
> 
> >        <para>
> >         Improve optimization of self-joins (Tom Lane)
> >        </para>
> >       </listitem>
> 
> > I don't think that's an accurate summary of those two items.  It's
> > true that they could make self-joins more efficient, but my reading is
> > that it would only do so if the self-join happened to use the ctid
> > column.
> 
> Yeah.  I think Bruce misread the commit messages, which commented that
> joining on TID is only likely to be useful in a self-join.
> 
> > So I think that this should probably be changed to say something like
> > "Improve optimization of self-joins on ctid columns" or "Improve
> > optimization of joins involving columns of type tid."
> 
> The latter seems fine to me.

I have updated to use the later wording.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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