[Zope-DB] Dynamically generate sql-query in ZSQL Method
Matthew T. Kromer
matt at bane.mi.org
Thu Apr 8 19:32:58 EDT 2004
On Apr 8, 2004, at 12:22 PM, Ian Bicking wrote:
> I had bad dreams last night -- literally -- thinking about what this
> means to all the code I've written or maintained in Zope, and anything
> that involves a side-effect.
Unfortunately, "side effects" get left by the wayside in the
documentation (or, one might say "what documentation?"), but there are
a few hotspots in Zope where a side effect can really bite you in the
Consider the security machinery, which secures the *values* you try to
work with. If your function is not protected with the same permissions
as your results, your function may run, but then the results may not
be visible by the user. Normally your function doesn't have any side
effects, but if it does... well, that's another spot you can get bitten
(really, only if the side effects cause Bad Things to happen to
> Just when you think you've found a pattern of application development
> in Zope that works okay -- even if it's not the Right Way or a
> sophisticated Zope way of managing things -- Zope turns around and
> punches you in the gut. Damn.
> Well, thank's for correcting me, even if you are the bringer of bad
> news ;)
Most of the problems arise due to the requirement to do things "the
Zope way" which are often easy, but nonobvious to people used to
working with more traditional systems. If you're used to having to
commit transactions to an RDBMS, you're caught by surprise when Zope
does it for you.
Note that under very sophisticated areas, Zope objects can support a
conflict management interface to resolve ConflictErrors without
retrying the request. However, every conflicting object has to support
the protocol, or else the whole transaction has to be re-run anyway,
and this doesn't address Read conflicts (which occur when data you read
to start your transaction have changed by the time you commit).
For the most part, the Zope automatic integration with RDBMS
transactions is a GOOD thing. Its only when you want to separate the
two that you run into some difficulties.
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