#14068: Fixture loading issue with multi database setting
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Reporter: linovia | Owner: nobody
Status: reopened | Milestone:
Component: Serialization | Version: 1.2
Resolution: | Keywords:
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by russellm):
* component: Uncategorized => Serialization
* stage: Unreviewed => Accepted
Comment:
Now I understand the error case. The rollback isn't the actual problem.
The error here is that there is now a difference between the number of
objects in a fixture and the number of objects that are loaded into a
given database.
If an error is found, it is rolled back because individual fixtures can be
interdependent - objects in one fixture can reference objects in another.
This means that if one fixture file has an error, the entire fixture setup
must be called into question.
If a fixture contains no objects, it is an error. This is well
established Django behavior that exists because certain serializers don't
distinguish between an unparseable fixture file and an empty fixture file.
In order to catch the error case, we need to raise an error if a fixture
exists, but is "empty". This doesn't cause an error in the test, but it
does cause many error messages to be raised to stderr.
The problem introduced by multi-db is that if your router has an
allow_syncdb definition, it's possible for a fixture to have valid data,
but none of those objects will be loaded into the database. However, the
object count is only incremented when an object is actually loaded, not
when it is parsed, so a fixture is reported as "empty" when no objects are
loaded, rather than when no objects actually exist.
The fix for this is fairly easy; I should be able to commit a patch
shortly.
As a side note; this problem can also be avoided using the per-database
fixtures I described when I closed the ticket earlier. If a fixture
nominates the fixture 'foo', and you provide 'foo.default.json' and
'foo.legacy.json', then only the relevant fixture will be loaded onto a
given database.
--
Ticket URL: <http://code.djangoproject.com/ticket/14068#comment:7>
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