[Zope] Is data.fs corrupted?

[seb bacon]

Could I just butt in here and try and clarify what I've understood from
this thread so far?  I'm feeling a bit dumb about it but I'd really like
to sort it out.

1) This problem is definitely a programming error
2) It arises when a product has a component which isn't 'registered' as
a zope object, so it's not cleaned up when the product is deleted

Is that right?  What would 'registered as a zope object' mean in this
situation?  Are there any other circumstances under which you end up
with orphaned instances?  *how can it be fixed?*

What I really don't understand is why seemingly unrelated products fail
as a result of the orphan instances.  Is is because new products are
trying to get an oid which happens to be used by the orphan?

If so, I don't think it's really so wrong to call this ZODB corruption,
although I take your point about the ZODB being stable.  In your perl
analogy, it's as if you are using two tables to create a parent / child
, one to many relationship.  You then deleted a parent row but forgot to
delete the corresponding child rows.  You data is now corrupted. 
True to your analogy, this arises in sloppy programming,
not in Oracle or whatever.  However, when you create the tables in
Oracle, you can place constraints on the tables so enforce the integrity
of your data, to protect against this kind of programming.  In a similar
way, I think it's too easy to end up with corrupted data in the ZODB.
Or perhaps I'm just particularly unlucky in the products I choose to
use?   

cheers,

seb
 
> 
> I'd argue that the ZODB is a very independent component of Zope, and it
> shouldn't be blamed for this.  Devil's advocate question:  if your Perl
> application failed because it couldn't find a record in an Oracle database,
> would you immediately chalk this up to database corruption and Oracle?
> 
> We do clearly need to work on Zope tools to make it easier to find and clear
> "orphaned" instances in the ZODB.  We should also try to weed out the
> programming errors which cause interdependencies of seemingly unrelated
> components of the same Zope instance that cause failures like this.
> Transactions are only tangentially related to this issue (I'm not sure how
> the "Added globals" transaction 'referred to' the "Installed product
> DemoPortal" transaction in your example, BTW).
> 
> BTW, I'm being sort of pedantic because when people hear "ZODB" and
> "corruption" in the same sentence, they tend to get scared and think of ZODB
> as "unstable" which is really not the case... most purported "ZODB
> corruption" issues are caused by programming errors in Products.  This has
> been the case for at least every one but one (the >2G pointer bug) that I've
> personally seen.
> 
> ----- Original Message -----
> From: "Bill Welch" <bill@carbonecho.com>
> To: "Chris McDonough" <chrism@digicool.com>
> Cc: <zope@zope.org>
> Sent: Wednesday, November 08, 2000 2:59 PM
> Subject: Re: [Zope] Is data.fs corrupted?
> 
> 
> > In my case, I couldn't import DemoPortal.zexp or Wizard.zexp from PTK
> > because oid 1377 was already in use. The pickle dump that followed
> > contained references to ZDiscussions, which I had deleted some time
> > before.
> >
> > After deleting the offending products and their directories, restarting
> > zope, and packing, I ran tranalyzer -r on my problem Data.fs. I found that
> > the problem oid was in this transaction:
> >
> > "/Control_Panel/Products/manage_importObject
> >
> > import into /var/lib/zope/var/Data.fs from
> > /var/lib/zope/import/ZDiscussions.zexp"
> >
> > referred to by this transaction:
> >
> > "Installed product DemoPortal"
> >
> > in turn, referred to by this tranaction:
> >
> > "Added Globals"
> >
> > I think ZODB corruption when I see a record in one product refer to
> > a record in an independent product and when the transaction of a deleted
> > product doesn't go away.
> >
> > On Wed, 8 Nov 2000, Chris McDonough wrote:
> >
> > > > I think it is ZODB corruption.
> > >
> > > This is very unlikely.  What makes you think this?
> >
> >
> >
> 
> 
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