#27974: Degraded performance when rendering ChoiceField with lots of options and
DEBUG=True
-------------------------------------+-------------------------------------
Reporter: karyon | Owner: kapil
Type: | garg
Cleanup/optimization | Status: assigned
Component: Template system | Version: 1.11
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 1 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by kapil garg):
There are certain problems because of caching.
1. cycle tag does not work in included template in a for loop just like
this bug [https://code.djangoproject.com/ticket/23516 ifchanged bug] . The
following patch seems to resolve the issue but it raises problem 2.
{{{
diff --git a/django/template/defaulttags.py
b/django/template/defaulttags.py
index e2be85b..3d6832e 100644
--- a/django/template/defaulttags.py
+++ b/django/template/defaulttags.py
@@ -74,10 +74,11 @@ class CycleNode(Node):
self.silent = silent
def render(self, context):
- if self not in context.render_context:
+ state_frame = self._get_context_stack_frame(context)
+ if self not in state_frame:
# First time the node is rendered in template
- context.render_context[self] =
itertools_cycle(self.cyclevars)
- cycle_iter = context.render_context[self]
+ state_frame[self] = itertools_cycle(self.cyclevars)
+ cycle_iter = state_frame[self]
value = next(cycle_iter).resolve(context)
if self.variable_name:
context.set_upward(self.variable_name, value)
@@ -89,7 +90,20 @@ class CycleNode(Node):
"""
Reset the cycle iteration back to the beginning.
"""
- context.render_context[self] = itertools_cycle(self.cyclevars)
+ state_frame = self._get_context_stack_frame(context)
+ state_frame[self] = itertools_cycle(self.cyclevars)
+
+ def _get_context_stack_frame(self, context):
+ if 'forloop' in context:
+ return context['forloop']
+ else:
+ return context.render_context
}}}
2. Nodes will share same state on multiple calls to include same template.
Currently i can verify this for Cycle and Ifchanged nodes. The reason is
that these nodes use "self" as a dictionary key to store their state and
caching prevents generating new nodes on multiple include calls. One
solution i can think of to solve this problem is to use "self" as
dictionary key for template caching as this will create a new cache for
each include node but this will lose the benefit of caching when there are
100 hardcoded include tags instead of being in a forloop.
These issues are related to caching so should we handle these on this
ticket or create a new ticket ?
--
Ticket URL: <https://code.djangoproject.com/ticket/27974#comment:10>
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