it's likely a bug. It looks like you've done some investigation already. I don't offhand have any understanding of the issue either, I would need to build up a reproduction case and then stare at it for several hours to figure out what's happening. So first step is if you can make a bug report at https://bitbucket.org/zzzeek/alembic/issues?status=new&status=open. Creating a test case is elaborate here, the graph you have above is likely enough to get started. The next step, which I can do, or you are welcome to work on if you have the motivation, is to create a test of this case in tests/test_version_traversal.py, similar to a test like this one: https://bitbucket.org/zzzeek/alembic/src/b702e057aeaa640c03232c77405dc5415ac8a670/tests/test_version_traversal.py#lines-557
these bugs are often hard to fix, so I would need to find some time to work on it. if you have a workaround for now that would be good. On Mon, May 28, 2018 at 11:13 AM, Lucas Kahlert <lucas.kahl...@gmail.com> wrote: > Hallo, > > we are using Alembic in a rather big project with various database revisions > and stumbled over a problem with diamond-shaped branch-merges. > > We have the following diamond-shaped dependency tree with three branches: > > "master" Branch > "addon 1" branch > "addon 2" branch > > The graph looks as follows: > > | | | > | a | > | . | . | > | . | . | > |. | .| > x1 | y1 > |. | .| > | . | . | > | . | . | > | b | > | | | > | | | > x2 c y2 > > Straight lines represent down_revision and dotted lines mean depends_on > relationships. The addon branches should not be merged into the master > branch. Hence, we use the depends_on directive as described in the Alembic > docs Branch Dependencies.We have various constructs of this shape in our > dependency graph. > > If we run alembic upgrade heads, we get an KeyError when applying the > "Merge" migration: > > File "/home/lucas/dev/torql/api/torql/migrations/env.py", line 115, in > <module> > run_migrations_online() > File "/home/lucas/dev/torql/api/torql/migrations/env.py", line 109, in > run_migrations_online > context.run_migrations() > File "<string>", line 8, in run_migrations > File > "/home/lucas/dev/torql/.venv/lib/python3.6/site-packages/alembic/runtime/environment.py", > line 797, in run_migrations > self.get_context().run_migrations(**kw) > File > "/home/lucas/dev/torql/.venv/lib/python3.6/site-packages/alembic/runtime/migration.py", > line 319, in run_migrations > head_maintainer.update_to_step(step) > File > "/home/lucas/dev/torql/.venv/lib/python3.6/site-packages/alembic/runtime/migration.py", > line 486, in update_to_step > self._delete_version(delrev) > File > "/home/lucas/dev/torql/.venv/lib/python3.6/site-packages/alembic/runtime/migration.py", > line 437, in _delete_version > self.heads.remove(version) > KeyError: 'a' > > Alembic cannot delete the branchpoint revision because it is not included in > the heads set of the alembic.runtime.migration.HeadMaintainer instance. > > The problem can be solved by inserting a "Noop" revision between the Branch- > and Mergepoint: > > | | | > | a | > | . | . | > | . | . | > |. | .| > x1 noop y1 > |. | .| > | . | . | > | . | . | > | b | > | | | > | | | > x2 c y2 > > Can someone explain the problem to us or is this a bug in Alembic? > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy-alembic" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy-alembic+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sqlalchemy-alembic" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy-alembic+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
