On Sat, Jun 13, 2015 at 3:53 PM, Peter Geoghegan <p...@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=8xm3fvcf1x9dlsvd3wvbt1...@mail.gmail.com#CAM3SWZRRCs6KAyN-bDsh0_pG=8xm3fvcf1x9dlsvd3wvbt1...@mail.gmail.com -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
