Re: release notes: tids & self-joins

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.

            regards, tom lane