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PODuplicate save in Django transaction causing InternalError instead of IntegrityError
 

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    <p>I am using PostgreSQL as my backend with psycopg2, and I'm noticing something that seems strange to me. My set up is as follows:</p> <pre><code>class ParentModel(models.Model): field1 = models.IntegerField() class ChildModel(ParentModel): field2 = models.IntegerField(unique=True) </code></pre> <p>When I try to save a ChildModel object with a duplicate field2 from the shell, I get an InternalError instead of an IntegrityError, but <em>only</em> if the save is done in a transaction.commit_on_success block like so:</p> <pre><code>with transaction.commit_on_success(): newObj = ChildModel(field1=5, field2=10) # Assume that a ChildModel with field2 == 10 exists </code></pre> <p>Outside of the transaction block, I get an IntegrityError, as I would expect. </p> <p>When running inside view code, I always get the InternalError following the failed update even using savepoints:</p> <pre><code>try: sid = transaction.savepoint() newObj = ChildModel(field1=5, field2=10) # Assume that a ChildModel with field2 == 10 exists transaction.savepoint_commit(sid) except IntegrityError: transaction.savepoint_rollback(sid) except InternalError: transaction.savepoint_rollback(sid) ... other stuff ... # raises InternalError on next database hit </code></pre> <p>Same thing happens if I do it within a commit_on_success transaction with block, instead of using savepoints. I have TransactionMiddleware installed and I am not running PostgreSQL in autocommit mode. </p> <p>I can avoid the situation by simply checking to make sure the duplicate object doesn't exist, but I want to udnerstand what's going wrong with my understanding of Django transactions. What gives?</p>
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