[Django] #23364: sql_queries from debug template context processor always empty
Django
-------------------------------+--------------------
Reporter: Markush2010 | Owner: nobody
Type: Bug | Status: new
Component: Uncategorized | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+--------------------
The `sql_queries` template context variable should propagated with all the
queries from `connection.queries`. However, this list seems to be always
empty:
{{{#!python
# django.core.context_processors
def debug(request):
"Returns context variables helpful for debugging."
context_extras = {}
import ipdb; ipdb.set_trace()
if settings.DEBUG and request.META.get('REMOTE_ADDR') in
settings.INTERNAL_IPS:
context_extras['debug'] = True
from django.db import connection
context_extras['sql_queries'] = connection.queries
return context_extras
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/23364>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
Reporter: Markush2010 | Owner: nobody
Type: Bug | Status: new
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by aaugustin):
* needs_better_patch: => 0
* needs_docs: => 0
* component: Uncategorized => HTTP handling
* needs_tests: => 0
* stage: Unreviewed => Accepted
Comment:
This is interesting.
Here's the relevant template from the sample project. `mymodels` is a
queryset and it isn't evaluated yet. `sql_queries` is set to
`connection.queries` in the `debug` context processor.
{{{
{% for mymodel in mymodels %}
<li>{{ mymodel.foo }}</li>
{% endfor %}
<pre>
{{ sql_queries }}
{{ sql_queries|length }}
</pre>
}}}
In Django 1.7, `connection.queries` is a list that gets updated with each
new database query. If you print the list in the context processor, it's
empty. But by the time you reach `{{ sql_queries }}` in the template, `{%
for mymodel in mymodels %}` has triggered a query, and `{{ sql_queries }}`
contains that query.
In Django pre-1.8, `connection.queries` is a snapshot of the ring buffer
that prevents unlimited memory consumption in long running processes. Once
the snapshot is made, it isn't updated with new database queries. As a
consequence, it's still empty when reaching `{{ sql_queries }}` in the
template.
I'm not sure what to do. Since it's common to have database queries
triggered by templates in Django projects, this unintentional change of
behavior will be considered a regression by most users. But having `{{
sql_queries }}` return different values depending on where you put it in
the template isn't a good API either.
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Ticket URL: <https://code.djangoproject.com/ticket/23364#comment:1>
Django
Reporter: Markush2010 | Owner: nobody
Type: Bug | Status: new
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Markush2010):
* cc: Markush2010 (added)
--
Ticket URL: <https://code.djangoproject.com/ticket/23364#comment:2>
Django
Reporter: Markush2010 | Owner: nobody
Type: Bug | Status: new
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by bpeschier):
* has_patch: 0 => 1
Comment:
Made sql_queries lazy and added tests for the debug context processor:
https://github.com/bpeschier/django/compare/ticket_23364
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Ticket URL: <https://code.djangoproject.com/ticket/23364#comment:3>
Django
Reporter: Markush2010 | Owner: aaugustin
Type: Bug | Status: assigned
Component: HTTP handling | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by aaugustin):
* owner: nobody => aaugustin
* status: new => assigned
Comment:
Looks good! I'll take it from there.
--
Ticket URL: <https://code.djangoproject.com/ticket/23364#comment:4>
Django
Reporter: Markush2010 | Owner: aaugustin
Component: HTTP handling | Version: master
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Aymeric Augustin <aymeric.augustin@…>):
* status: assigned => closed
* resolution: => fixed
Comment:
In [changeset:"eacf244506d8b7e6dd6483834ea122fec864da85"]:
{{{
#!CommitTicketReference repository=""
revision="eacf244506d8b7e6dd6483834ea122fec864da85"
Converted sql_queries into a lazily evaluated list.
Fixed #23364. Thanks Markush2010 for the report.
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/23364#comment:5>