On Thu, 2009-04-02 at 21:19 +0300, Heikki Linnakangas wrote: > The data type itself is quite trivial. It's all the operators that are > more difficult to implement, and also immensely useful. That part is > still incomplete.
Can you please let me know what you find lacking (note: the SVN repo is the most current one)? I've implemented a pretty standard set of operators, and a GiST opclass to make things like overlaps, etc., indexable. I have not yet implemented temporal join. > I'd recommend a book called Temporal Data and the > Relational Model by C.J. Date, Hugh Darwen and Nikos Lorentzos for > anyone interested in this topic. That book gives a guideline on how the > data type and operators should behave. Agreed! That is a _very_ good book, and it's what I based my PERIOD type on (I used to call it t_interval because I agree with Date that's a better word -- but the conflict with SQL was too great so I changed it). > I'd love to see that implemented. I volunteer to mentor if someone wants > to tackle it. A big open question is whether we do new syntax, and if so, what. A lot of the literature for temporal types out there (from people basing their suggestions on SQL, like Snodgrass, et al., not C.J. Date) suggests syntax extensions which seem pretty specialized and unnecessary to me, but perhaps convenient. The only thing I really think needs better syntax is a constructor that can easily represent [ ), [ ], ( ), ( ] -- i.e. inclusive/exclusive. Right now I have 4 functions to do that, but it's awkward and overly verbose. In a related topic, an index that can implement a non-overlapping constraint is important to temporal databases. I have done some implementation work on this already, based on my proposal here: http://archives.postgresql.org//pgsql-hackers/2008-06/msg00404.php and I have adjusted my design to address some of the concerns Tom brings up here: http://archives.postgresql.org//pgsql-hackers/2008-06/msg00427.php I already have some code written, so if anyone else is thinking of working on this please contact me first. I will post my progress in the next couple weeks. Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
