id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
19920	DatabaseError exceptions in _commit, _rollback, etc.	Aymeric Augustin	nobody	"#14223 unified the IntegrityError exceptions raised in _commit.

For consistency, Django should also unify DatabaseError exceptions raised in _commit and _rollback.

To be fully consistent, Django should also wrap exceptions in savepoint-related methods.

I'm going to need this for error handling in persistent connections.

----

With the current approach this is going to result in a lot of duplicated code:

{{{
            try:
                # do stuff
            except Database.IntegrityError as e:
                six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
            except Database.DatabaseError as e:
                six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
}}}

A better solution would be to abstract this pattern into a decorator.

----

A less magical alternative is to make the exceptions attributes of the database wrapper. This would allow code such as:

{{{
for conn in connections.all():
    try:
        conn.rollback()
    except conn.DatabaseError:
        pass
}}}

This solution seems more robust to me.

It's suggested as an extension by PEP249: http://www.python.org/dev/peps/pep-0249/#connection-error

It's more backwards compatible with the current code because it doesn't require changing the type of some exceptions.

It avoids problems with catching the ""wrong"" DatabaseError (Django's vs. the database adapter's). This is an easy mistake, and database exceptions are very hard to test — one cannot shut down the database during tests!

I'm mostly logging this alternative for posterity, because Django made a different choice long ago, and reversing it would be complicated — all the more since a non PEP-249 exception was introduced in the hierarchy: ProtectedError, see https://docs.djangoproject.com/en/dev/ref/exceptions/#transaction-exceptions"	Bug	closed	Database layer (models, ORM)	dev	Normal	fixed			Unreviewed	1	0	0	0	0	0