ok... sounds good...
marcf
|-----Original Message-----
|From: [EMAIL PROTECTED]
|[mailto:[EMAIL PROTECTED]]On Behalf Of David
|Jencks
|Sent: Thursday, June 14, 2001 5:05 PM
|To: [EMAIL PROTECTED]
|Subject: RE: [JBoss-dev] No storeEntity before ejbFind<METHOD>
|
|
|Hi,
|
|Hey guys, think a minute. What transaction isolation means is _other_
|transactions can't see your work until you commit. Of course _your_
|transaction can see everything you've done. If you're working with say the
|oracle interactive interface and insert a record in a table, if you query
|the table you can see it right away, you don't have to commit first.
|_other_ people can't see it until you commit. This has nothing to do with
|xa or anything else.
|
|[although there is a related issue with "tightly coupled" and "loosely
|coupled" transaction branches in xa: loosely coupled means different
|branches of the same transaction can't see each others work. This should
|only arise when several transaction managers are using the same global
|transaction against the same resource, and the XAResources can't agree that
|they are using the same resource. Maybe this is what you guys are thinking
|of, but this should only be a potential problem with distributed jboss]
|
|I'm pretty sure someone else complained about this a couple of weeks ago,
|although I can't find the reference - they were modifying an entity, then
|doing a finder method returning a collection including the "just modified"
|bean, except they weren't seeing the modifications.
|
|In my opinion, if this requirement was not present in ejb 1.1, is was a
|serious requirements bug, encouraging logically inconsistent behaviour from
|the container.
|
|Thanks, Bill.
|
|david jencks
|
|On 2001.06.14 15:49:34 -0400 marc fleury wrote:
|> |I have been working with databases for a long time,
|> |and particularly with Oracle, I am not aware that this
|> |can happen, whether in transaction or not, before
|> |commit, nobody can see the updated table period in the
|> |database..
|>
|> well that is my point precisely, it seems to imply that the updates
|> "before
|> the commit" are seen by connections enrolled in the SAME transaction
|> THROUGH
|> THE DATABASE.... and frankly I am a bit skeptical as to the level of
|> support for these features in the db or even if they exist at all or are
|> just "wishful features" (heck they don't even support 2pc and xa
|> right)...
|>
|> so this smells of "teen spirit" to me... by requiring "inflight"
|> visibility
|> of the changed records they put a difficult requirement on the db drivers
|> and I don't see it working well.
|>
|> They could have just required lock steps, as in first commit the changes
|> (and the db can follow that semantic) and then issue your findBy as just
|> another query...
|>
|> I am no db expert (they are rare these days) but it strikes me as a
|> misguided requirement.
|>
|> Bill for example couldn't you get the same functionality with the
|> serialiazed commits? Is this functionality that you couldn't get
|> otherwise?
|> you are the first one to require this feature (and you are savvy enough
|> to
|> scratch your itch so that is cool but still I wonder...)
|>
|> but the REAL question is "is it true that you cannot see changed tables
|> from
|> a connection participating in the SAME transaction that changed it in the
|> first place?"
|>
|> regards
|>
|> marcf
|>
|> |
|> |I don't know much about XA, it having its own set of
|> |rules though.
|> |
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