On Wed, Jun 18, 2008 at 5:05 AM, David <wizzardx@xxxxxxxxx> wrote: > I haven't used them before, but I like the idea of never > deleting/updating records so you have a complete history (a bit like > source code version control). Well depending on what kind of temporal behavior you are modeling, there may be cases where you will update a temporal segment. That is why the bi-temporal tables were introduced. They track the changes that are many to another tables temporal segment. > How well do temporal databases work? They work really well. But the are alot of work to create and because of this changing their structure is also alot of work. > Do RDBMS (ie Postgresql) need > add-ons to make it effective, or can you just add extra temporal > columns to all your tables and add them to your app queries? Postgresql contains most of the features needed to make a temporal database. However, the hard part of temporal database is developing your own referential integrity constraints that would need to exists between related entity time line tables. > Does this > increase app complexity and increase server load a lot? I would expect that it would add abit, since you need to remember that you not really deleteing a record or updating. you are only altering and adding timeline segments. > Are there Python libraries which simplify this? (eg: add-ons for > Elixir or SQLAlchemy). Not to sure. > Or should apps all implement their own 'temporal data access' module, > which transparently uses the current date & time until queried for > historical data? Currently there is a project to add temporal functionality to postgresql. Currently is doesn't add any referential integrity. It only adds special temporal data types and functions for evaluating temporal comparisons. http://pgfoundry.org/projects/temporal/ Although there is a desire to add RI to PG. However, this functionality would need to be directly added to the core of postgresql. It will probably be a long while before this happens. -- Regards, Richard Broersma Jr. Visit the Los Angles PostgreSQL Users Group (LAPUG) http://pugs.postgresql.org/lapug
