[Zope] sub-transaction in DTML?

[Jay, Dylan]

> -----Original Message-----
> From: Michel Pelletier [mailto:michel@digicool.com]
> Sent: Wednesday, March 15, 2000 4:19 AM
> To: Jay, Dylan
> Cc: 'zope@zope.org'
> Subject: Re: [Zope] sub-transaction in DTML?
> 
> "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.

but having a DB manage my user data is not an unresonable requirement on a
site.
 
> > 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

why do I need a concept of a sub-transaction. Is there just something that I
can call that will commit all changes up until a certain point and then
begin the new transaction? I realize this will break the transaction model
to some extent but if the method is long and each iteration is indepedent
this seems a reasonable thing to do.

> '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.

To do the work using a shorter query would mean breaking the method up into
chunks and then having to call it multiple times which is pretty ugly.

Tell me how to get a concurrent DA on NT without breaking the bank and I'll
do it.
So far I have:

- MS SQL server - Apparently sybaseDA will work but havn't been able to
compile it on NT. You need certain files from sybase I believe.

- SQLAnywhere - same problem as above.

- Oracle - too expensive.

- MySQL - No transactions.

- PostgresSQL - Got the NT binaries but can't get it working. Also can't
compile the postgresDA.

- ODBC - Not level 3.

As far as I can tell the above represents all the options I have open to me.





> -Michel
>