[Buildbot] #2590: Use Alembic instead of SQLAlchemy-Migrate

[Buildbot trac]

#2590: Use Alembic instead of SQLAlchemy-Migrate
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Reporter:  dustin        |       Owner:
    Type:  project-idea  |      Status:  new
Priority:  major         |   Milestone:  0.9.+
 Version:                |  Resolution:
Keywords:  database      |
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Comment (by stibbons):

 Why do you want to migrate all script to alembic vs why not freeze one
 point? Do you want users to be able to migrate from buildbot 0.8 (migrate)
 to 0.9 (alembic)?
 I don't think this would be an issue, anyaway.

 What do you call "monkeypatch"? It generates upgrade/downgrade method by
 comparing your model to the current state of the database, but there are
 lot of stuff he is not able to see: column rename (it does a add/remove),
 action in enums,...

 For your migration script translation, I would use the same "dialect"
 (import sqlalchemy as sa) just the pattern of the script will be the same.

 I agree with you statement on upgrade-master, however I still wonder if it
 is a usecase it worth adding this complexity. If you want to protect
 against bad use, this is a way BUT this wont protect against everytime, I
 would say it is rare case. I don't remember the number of time I had to do
 "upgrade-master" on 0.8 in order to fix the deadly message on buildbot
 start. Result, we now execute upgrade-master everytime and it works like a
 charm in our prod for a while. Anyway, let's assume it is a design choice.

 back to alembic, I can give a try if you want, to have something real to
 debate on.

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Ticket URL: <http://trac.buildbot.net/ticket/2590#comment:7>
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