45 lines
1.3 KiB
Org Mode
45 lines
1.3 KiB
Org Mode
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#+TITLE: Silly django confusion
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#+DESCRIPTION: Think about this next time...
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I'm setting up a testing environment for work, using fixtures to save
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and load test data and I got a little stumped by something I ran into.
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I had exported one of the database tables we use to a json file that I
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was going to import into a fresh new database to test with. When I
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imported it everything seemed fine, except when looking at the actual
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page. So this is what I found:
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#+BEGIN_SRC sql
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SELECT * FROM app_table;
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=> 3 rows of data
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#+END_SRC
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#+BEGIN_SRC python
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from app.models import Table
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Table.objects.count()
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=> 3
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Table.objects.all()
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=> []
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#+END_SRC
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This is weird. So I looked at the ~django.db.connection.queries~
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property and I realized that it was doing a join since the model
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subclasses another:
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#+BEGIN_SRC python
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from django.db import models
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from app.models import SuperTable
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class Table(SuperTable):
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field1 = models.CharField(max_lenth=200)
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#+END_SRC
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Which, of course, means that in order to get the complete ~Table~
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instance, the related ~SuperTable~ instance is also required, but in
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order to do a ~COUNT~ of ~app_table~ it isn't necessary. And that's
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where the inconsistency came from, now that I've also copied the
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contents of ~SuperTable~ everything is fine again.
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