[Zope] sub-transaction in DTML?

[Michel Pelletier]

"Jay, Dylan" wrote:
> 
> I have a method that takes a long time on a system that uses a level 2 DA,
> therefore it blocks the entire site

To be more specific, it blocks all other requests through that and other
level 2 DAs.  Non SQL related calls and level 3 DA calls will not get
blocked.

> (it also uses UserDB so everything uses
> the DB).

Yeah that kinda puts a damper on the whole site... but that's just
because every access is now an SQL related call.

> How can I put sub-transactions in my DTML to give others a chance
> to use the site?

This is not what ZODB sub-transactions do.  Even if you were using a
relational database that has a notion of sub-transactions (Oracle has
'nested transactions' for example) that would not stop the blocking (of
course if you were using Oracle you would be using a level 3 DA...).
ZODB sub-transactions allow changed objects to get flushed to a temp
filestorage so that you can accumulate more object changes then can fit
in virtual memory.  There is no mapping of sub-transaction semantics to
any of the DAs.  In fact, if I remember correctly using ZODB
sub-transactions with SQL methods is Not A Good Thing.  I don't remember
the exact details.

Solutions?  Execute a shorter query or upgrade to a concurrent DA.

-Michel