[postgis-devel] Versioning and Historyu

George Silva georger.silva at gmail.com
Sat Dec 5 06:03:06 PST 2009

All the tips and considerations are excellent Ragi, but same as
Regina, i'm thinking about Applications, not just database logic.

A set of rules/triggers would be interesting to start propagating the
changes to child versions, but in some place everything gets hairy,
and that's where the application code must jump in and help.

Not everything can be enforced through the database, and i imagine a
system where the user gets to choose the working version.

If something would be carried out with rules and triggers that means
that the user should edit the parent table (INSTEAD OF), but that
would cause a great deal of confusion, because he would need to load
the main version on a GIS software and edit it from there. Also, when
editing he would only see changes in the versioned tables.

A great deal of system logic needs to be considered, in the aspects of
choosing version, showing the correct changes, etc. Also i do _not_
want to duplicate all records for each version. This would be much
easier, but impratical for most serious systems.

Thanks for your thoughts and i'm still listening.



On Fri, Dec 4, 2009 at 6:49 PM, Paragon Corporation <lr at pcorp.us> wrote:
>  >  And a comment:
>  >  Think *Views*! ... hiding this complexity in views will make your life
> easier plus it will not need changes in clients. Clients connecting to a
> PostgreSQL DB can use the tables like they normally do, and clients that
> want to leverage the versioning aspect of it can use the versioning stored
> procedures (i.e set_current_version('myversion')).
>  >  My two cents,
>  >  - Ragi
> Just a note.  Views are great, but to many applications they don't see
> primary keys and when they don't sadly views appear as read-only even if you
> make them updateable.  Just something to consider, that they are sadly not
> as transparent as they should be. Think geoserver for example.
> Regina
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George R. C. Silva

Desenvolvimento em GIS

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