Re: [Zope-dev] Possible performance problem in Page Template engine?

[Andreas Jung]

--On 27. Oktober 2007 00:33:42 +0200 Christian Scholz <[EMAIL PROTECTED]> 
wrote:



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!



The evaluate() call within _handleText() is a culprit from my refactoring.
However I see this code only on the trunk. It is not contained on the 2.10
branch. Anyway...I removed the culprit from the trunk and everything should 
be fast again.


Andreas



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[Zope-dev] Possible performance problem in Page Template engine?

[Christian Scholz]

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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