Hi everybody!

When I was trying to fix portlets in Plone I was wondering why the render() method of my portlet actually gets called multiple times.


After a bit of investigation I ended up in the Five product in browser/providerexpressions.py where provider expressions also seem to be called twice for each provider statement.

The problem seems to be in Products/PageTemplates/Expressions.py in line 199/200 (in Zope 2.10.4):

def evaluateStructure(self, expr):
        """ customized version in order to get rid of unicode
            errors for all and ever
        """
        text = super(ZopeContext, self).evaluateStructure(expr)
        return self._handleText(text, expr)

This construct seems to evaluate expr twice. One time in evaluateStructure() of the super class which is basically a call to self.evaluate(expr) (to be found in zope/tales/tales.py around line 713:

    def evaluateStructure(self, expr):
        return self.evaluate(expr)

and then again in _handleText():

    def _handleText(self, text, expr):

        text = self.evaluate(expr)

        ...

I now tried to remove the evaluation of expr in handleText() and in a very simple test using ab on my site I got twice the speed!

I might be missing something here of course but if every expression is evaluated twice then this is of course huge performance drain. And of course this fix was just a quick idea without much understanding of the underlying engine (e.g. not knowing if _handleText() is also called from somewhere else etc.)

So any Page Template experts here who can confirm this?

cheers,

Christian


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