Re: [sqlalchemy] alembic: downgrade raises KeyError

Mon, 03 Aug 2015 16:02:32 -0700 


On 8/3/15 6:51 PM, Mike Bayer wrote:


On 8/3/15 4:59 PM, Dirk Makowski wrote:

Hi all,


after upgrading alembic to 0.7.7 and SQLAlchemy to 1.0.8, when I try 
to downgrade one step from head, I get the below KeyError. The 
allegedly missing key is the revision ID of head. It is correctly 
stored in the alembic table, and the file and its predecessor are 
also present.



I'm not able to reproduce any issue.   I'm using Python 3 like you are 
and even turning on PYTHONHASHSEED=random, I can upgrade, downgrade, 
-1, +1, whatever, does everything perfectly.   This is of course with 
a plain vanilla env.py file as i don't have your special libraries 
available.



Are you able to reproduce your issue using a brand new Alembic 
environment and using just these version files ?  there is nothing 
unusual here and you have a perfectly linear ordering.   The error 
message indicates the internal organization of revisions as it places 
them into dependency order is failing but I can't see how that would 
happen here.     Also, the 0.7 series has been out for months and if 
the revision logic were capable of failing on a perfectly straight 
line of files without even any branch or mergepoints, it seems like 
that would have been noticed.  I can simulate an internal condition 
that produces this stack trace, but I don't see how this condition can 
occur.



Also, what is the *exact* version of Python 3 you're using ?  Are 
there any .pyc files from the older Alembic 0.6.7 lying around in the 
virtual environment or is this a fresh environment ?


OK.   Here's what will cause this exactly:

sqlite> select * from alembic_version;
32f69b44319
32f69b44319


duplicate revisions in alembic_version.  Do you have that going on? If 
so, was that via manual intervention?  I'll add a protection for this 
that will prevent the issue but the alembic_version table should not 
have duplicate rows in it.

















Other commands however do find that key:

{{{
$ alembic -c etc/Morrigan/development/alembic.ini heads --verbose
Rev: 32f69b44319 (head)
Parent: 1644537aa7

Path: 
/home/dm/myprojects/Foo/alembic/versions/32f69b44319_20150714_feat_mdv_mgmt.py


20150714_feat_mdv_mgmt
    Revision ID: 32f69b44319
    Revises: 1644537aa7
    Create Date: 2015-07-20 14:52:40.227436
}}}

and

{{{
$ alembic -c etc/Morrigan/development/alembic.ini show  32f69b44319
Rev: 32f69b44319 (head)
Parent: 1644537aa7

Path: 
/home/dm/myprojects/Foo/alembic/versions/32f69b44319_20150714_feat_mdv_mgmt.py


20150714_feat_mdv_mgmt
    Revision ID: 32f69b44319
    Revises: 1644537aa7
    Create Date: 2015-07-20 14:52:40.227436
}}}

But downgrading gives:

{{{
$ alembic -c etc/Morrigan/development/alembic.ini  downgrade  -1
INFO  [alembic.migration] Context impl PostgresqlImpl.
INFO  [alembic.migration] Will assume transactional DDL.
Traceback (most recent call last):

  File "/home/dm/myprojects/atrial-py34-venv/bin/alembic", line 9, in 
<module>

load_entry_point('alembic==0.7.7', 'console_scripts', 'alembic')()

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/config.py", 
line 439, in main

CommandLine(prog=prog).main(argv=argv)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/config.py", 
line 433, in main

self.run_cmd(cfg, options)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/config.py", 
line 416, in run_cmd

    **dict((k, getattr(options, k)) for k in kwarg)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/command.py", 
line 193, in downgrade

script.run_env()

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/script.py", 
line 390, in run_env

util.load_python_file(self.dir, 'env.py')

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/util.py", 
line 244, in load_python_file

    module = load_module_py(module_id, path)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/compat.py", 
line 68, in load_module_py

    module_id, path).load_module(module_id)
  File "<frozen importlib._bootstrap>", line 539, in _check_name_wrapper
  File "<frozen importlib._bootstrap>", line 1614, in load_module
  File "<frozen importlib._bootstrap>", line 596, in _load_module_shim
  File "<frozen importlib._bootstrap>", line 1220, in load
  File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 1129, in _exec
  File "<frozen importlib._bootstrap>", line 1471, in exec_module

  File "<frozen importlib._bootstrap>", line 321, in 
_call_with_frames_removed

  File "alembic/env.py", line 97, in <module>
run_migrations_online()
  File "alembic/env.py", line 92, in run_migrations_online
context.run_migrations()
  File "<string>", line 7, in run_migrations

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/environment.py", 
line 738, in run_migrations

self.get_context().run_migrations(**kw)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/migration.py", 
line 302, in run_migrations

    for step in self._migrations_fn(heads, self):

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/command.py", 
line 182, in downgrade

    return script._downgrade_revs(revision, rev)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/script.py", 
line 315, in _downgrade_revs

    current_rev, destination)

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/revision.py", 
line 512, in iterate_revisions

    inclusive, assert_relative_length

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/revision.py", 
line 450, in _relative_iterate

inclusive=inclusive, implicit_base=implicit_base))

  File 
"/home/dm/myprojects/atrial-py34-venv/lib/python3.4/site-packages/alembic/revision.py", 
line 672, in _iterate_revisions

total_space.remove(rev.revision)
KeyError: '32f69b44319'
}}}

Thanks for your help,
Dirk
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