[Zope] Concurrency/Atomicity in ZSQL/ZOracleDA ?

[Renaud Guerin]

Hello,

I have a probably simple question, but got different opinions on the matter, 
and I'm seriously in need of a quick answer.

I need to make a ZSQL method that inserts data in a table this way:

1) first, generate a new ID with something like SELECT MAX(ID)+1 AS my_id 
FROM ... (using a sequence is not an option for me for various reasons)

2) then, INSERT with the ID previously generated ( is INSERT INTO ... VALUES 
(<dtml-var my_id>.... the right way to do this ?)

3) display my_id to the user for future reference.

First, I'm not sure how to do 3) : how do I pass my_id back to the original 
DTML document (which calls the ZSQL method with dtml-call) ?

Also (main question), is there something particular to do to ensure 
SELECT+INSERT is done in an atomic way that avoids concurrency 
problems ?

I know Zope starts and ends transactions with HTTP requests, but I'm not sure 
this implies the kind of read locking I need.


thanks a lot!
PS: please cc any answers.