[SQLObject] Catching exceptions

[Michel A. <ex...@wi...>]

Recently I had a thought on database exceptions. I am too lazy to repeat,  
so here is the transcript:

13:21 < exhuma> hmmm... I wonder.... When using turbogears, you generally  
also use SQLObject or
                 SQLAlchemy.
13:21 < exhuma> Which is good abstractionwise.
13:22 < exhuma> however.... The database exceptions get still raised  
"into" the controllers files.
13:23 < exhuma> But if you want to be DBMS-agnostic, you should not be  
required to import the different
                 database's exceptions for intercepting them
13:23 < exhuma> I mean, right now I ran into an exception in my app which  
comes from psycopg.
13:24 < exhuma> So I need to do something like "from psycopg import ...".  
If I then wanted to port to a
                 different DBMS I needed to rewrite those statements.
13:24 < exhuma> hummm... actually that's more an SQLObject issue I suppose  
;)


But let me clarify ;)

I like the simplicity of SQLObject. It's beautiful to work with. Main  
reason for that is that you can be really ignorant about the underlying  
database system. But one thing slipped through I guess. Let's say you run  
into an IntegrityError exception.  For example if you want to insert  
something that violates a unique-key constraint in the database. The  
exception that get's raised from the application is actually the exception  
 from the database module itself (be it MySQLdb, psycopg, or something  
else). So to catch those exceptions properly you have to either write  
something like "except MySQLdb.IntegrityError" or somewhere else "from  
MySQLdb import IntegrityError".But that means you would need to change the  
code every time you change the DBMS.

I beleive that for an abstraction framework like SQLObject it would be  
much better to have it raise it's own exceptions. So you could do "...  
except sqlobject.IntegrityError ..." and only make it raise other  
exceptions if it's not supported or known by SQLObject.

What do you think?


Best regards,

Mich