[Grok-dev] megrok.rdb updated

[Martijn Faassen]

Hi there,

I've started updating megrok.rdb, using the recent work done on 
zope.sqlalchemy, z3c.saconfig, and my now somewhat greater understanding 
of SQLAlchemy.

As a result, megrok.rdb has moved to a top-level directory in svn and 
now actually has a README.txt which is also a doctest:

http://svn.zope.org/megrok.rdb/trunk/src/megrok/rdb/README.txt

I also updated the rdbexample to make use of the new code, though it's 
rather hard to play with it as it has the horrible text-only screens 
instead of proper page templates:

http://svn.zope.org/grokapps/rdbexample/trunk

There is a lot that remains to be done.

* The directives need to become a lot stricter; right now it's too easy 
to do something wrong and get an obscure error. We need more validation, 
better default behavior, etc.

* It turns out that using auto-generated primary keys as a container key 
doesn't look possible: this primary key is not assigned yet by the 
database by the time the container can be used. This means containers 
need an important re-think as this destroys the only sensible default 
behavior I can think of right now. This is a big problem and we need 
some way around it - there often is no other column in a database table 
that can function as a key.

* it would be nice if we could have a default behavior for metadata, so 
that the rdb.metadata directive can be omitted entirely. Note that the 
rdb.metadata directive may not work properly yet on a module level; at 
least I haven't tested it yet.

* More work needs to be done in making database setup easier. While 
z3c.saconfig helps a lot, it's still setting up quite a bit to get the 
basic case working. I hope we'll eventually see a grokui.rdb which 
allows people to set up a database utility and connection parameters 
through the grok admin screens.

* actually automatically creating the tables in the database from the 
metadata is something we need some infrastructure for too. Right now in 
rdbexample I do this upon first traversal into the application. We could 
do it upon application add time perhaps, and also perhaps present a UI 
in grokui.rdb to let people refresh the database tables.

* I haven't even touched the part that generates a Zope 3 schema from 
database schemas; this code is nice to generate forms. This requires 
some more study of the various alternatives around, and SQLAlchemy 
itself (last time we looked at it we weren't able to retrieve the order 
of definition for columns in a table, which is rather important to show 
a nice form).

Regards,

Martijn