[ZODB-Dev] Re: false write conflicts

[Marius Gedminas]

On Wed, Mar 03, 2004 at 10:04:15AM +0000, Chris Withers wrote:
> Marius Gedminas wrote:
> 
> >I've seen a recommendation somewhere that it is better to write
> >
> >  self.attr[x] = y
> >  self.attr = self.attr      # notify Persistence that something changed
> >
> >than
> >
> >  self.attr[x] = y
> >  self._p_changed = True     # notify Persistence that something changed
> 
> Why is that?

I don't remember.  ;)

<googles>

It seems that I misremembered the suggestion -- it is better to use
_p_changed rather than attribute assignment:

  http://mail.zope.org/pipermail/zope3-dev/2002-September/002771.html

And I made another mistake as well: the persistence should be triggered
*before* modifying self.attr, not after (cf. the same thread).

Nevertheless there exists code somewhere in the wild that uses the first
idiom to trigger persistence.  Accidentally mixing this code with a
__setattr__ wrapper could introduce bugs.  It is probably very unlikely
in practice, but I like to point out such possibilities.

Marius Gedminas
-- 
Any sufficiently advanced technology is indistinguishable from a rigged demo.
- Andy Finkel, computer guy
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