On Thu, Aug 20, 2015 at 04:07:36PM -0700, Peter Geoghegan wrote:
> On Sat, Jun 13, 2015 at 3:53 PM, Peter Geoghegan <pg@heroku.com> wrote:
> > I think we should really address this. Attached patch adds a new
> > release note item for it. It also adds to the documentation that
> > explains why users should prefer varchar(n)/text to character(n); the
> > lack of abbreviated key support now becomes a huge disadvantage for
> > character(n), whereas in previous versions the disadvantages were
> > fairly minor.
> >
> > In passing, I updated the existing sort item to reflect that only
> > varchar(n), text, and numeric benefit from the abbreviation
> > optimization (not character types more generally + numeric), and added
> > a note on the effectiveness of the abbreviation optimization alone.
>
> A recent e-mail from Kaigai-san [1] reminded me of this item. I really
> think this limitation of char(n) needs to be documented along the
> lines I proposed here back in June. Benchmarks like TPC-H use char(n)
> extensively, since it's faster in other systems. However, PostgreSQL
> now has hugely inferior sort performance for that type as compared to
> text/varchar(n). This needs to be highlighted.
>
> [1]
http://www.postgresql.org/message-id/flat/CAM3SWZRRCs6KAyN-bDsh0_pG=8xm3fvcF1X9dLsVd3wVbt1pHw@mail.gmail.com#CAM3SWZRRCs6KAyN-bDsh0_pG=8xm3fvcF1X9dLsVd3wVbt1pHw@mail.gmail.com
I have applied the attached patch to document this in the data type docs.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
