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PODjango select_related with fields specified breaks over multiple one to one relationships
 

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  1. PODjango select_related with fields specified breaks over multiple one to one relationships
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    <p>I'm getting a weird error trying to select_related over multiple OneToOneField relationships, e.g. in the case where the target field is a grandchild subclass. I'd love someone to help me understand what's going on (or confirm that this is a bug in Django). </p> <p>Illustration:</p> <pre><code># models.py from django.db import models class A(models.Model): pass class B(A): pass class C(B): pass </code></pre> <p>Simple enough, right? Now I open the Django shell with a clean database:</p> <pre><code>&gt;&gt;&gt; C().save() &gt;&gt;&gt; A.objects.select_related('b__c') [] </code></pre> <p>Wait, what? Why is that queryset empty? A quick sanity check:</p> <pre><code>&gt;&gt;&gt; A.objects.select_related('b')[0].b.c &lt;C: C object&gt; </code></pre> <p>So why doesn't the select_related call work? Well, watch this:</p> <pre><code>&gt;&gt;&gt; A.objects.select_related('b__c').__iter__().next() ... Traceback (most recent call last): File "&lt;console&gt;", line 1, in &lt;module&gt; File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/query.py", line 107, in _result_iter self._fill_cache() File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/query.py", line 772, in _fill_cache self._result_cache.append(self._iter.next()) File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/query.py", line 273, in iterator for row in compiler.results_iter(): File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 680, in results_iter for rows in self.execute_sql(MULTI): File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 725, in execute_sql sql, params = self.as_sql() File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 58, in as_sql self.pre_sql_setup() File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 29, in pre_sql_setup self.fill_related_selections() File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 661, in fill_related_selections used, next, restricted, new_nullable) File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 617, in fill_related_selections chain = opts.get_base_chain(f.rel.to) File "/opt/webapps/asdf/lib/python2.6/site-packages/django/db/models/options.py", line 452, in get_base_chain % model._meta.module_name,) TypeError: 'b' is not an ancestor of this model &gt;&gt;&gt; </code></pre> <p>So, is this a Django bug, or am I not understanding something?</p>
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    1. COGiven the silence on this, I filed a bug: https://code.djangoproject.com/ticket/16572
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    2. COgot into exactly the same problem. strange behaviour, seems like a django bug indeed.
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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