Alembic - Use dates instead of revision

[ievgennaida]

I am facing conceptual difficulties in executing alembic based on the sequential revisions using modern delivery approaches.

Is your feature request related to a problem? Please describe.
We started to use delivery process based on GitFlow and almost every merge request is causing problems with alembic sequential revisions.

Ex:
Main DB has a revision 'A'

Ex: 3 Feature are developed on a separate branches and they are based on 'A'. Ex: 'A'->'B', 'A'->'C', 'A'->'D'
It's expected that developer will create a merge requests (GitFlow) and features will be automatically picked up, migration is started and feature is delivered.

For our project it's not a big deal if 'B','C','D' will be not strictly sequentially executed at the beginning while all 3 are based on the same release 'A' so it's suppose to be safe.

Now, with the revisions you need just a separate userstory to align all 3 features, so it's a manual step.

Describe the solution you'd like
To be honest I see it in a simpler way is just to make revisions based on date instead of the hash.
Please make a property just allowing to switch to the date and problem suppose to be gone.
In this case you also don't need to specify previous revision.
P.s. It can be used only for the particular usecase. For it's not a big deal if migration forward will be 'A' -> 'D', 'C', 'B' (based who delivered first)
and downgrade back will become sequential 'D' -> 'C' -> 'B'-> 'A' (based on date in alembic file)

Describe alternatives you've considered
Alternative is to manually merge features and files every time before the delivery that is really slowing us down.
Custom approach based on dates was used by me in a past and it was consistent.

Thank you for any suggestions.

[diegopasciuto]

+1
Same problem here

[zzzeek]

hi there -

I'm not sure I understand what this is asking for. you can use any revision identifier you'd like for a given revision by indicating the --rev-id argument to alembic revision:

alembic revision -m "my revision" --rev-id "2021-06-11 09:41:00"

if you'd like each revision to be fully independent of the others, then you give it a new head:

alembic revision -m "my revision" --rev-id "2021-06-11 09:41:00"  --head base

so that seems to be what you're asking for. but then, when you run "alembic upgrade", all these revs will be invoked in random order. Which seems to suggest perhaps you are looking for an alternative revisioning model that orders revisions strictly by timestamp and has no concept of a "down revision". if that's what you're looking for, that's not Alembic's model and you will need to implement your own solution. It's not generally a good assumption that the order of dependencies for database migrations has a 1-1 correlation to the specific timestamp that each was created, as different branches and merges may have been developed at interleaving times which dont correspond to the actual dependency chain for a database.

[iuadastra]

Can this be a default like in other similiar tools? For example here. It is much simpler to follow the history and see what and when changed

[CaselIT]

an most it could be a setting in alembic.ini.

overall there do not seem to be many requests to change how the revision id are generated, so I'm not in favour of changing the default
You can modify the file template to include the date here

alembic/alembic/templates/generic/alembic.ini.mako

Line 12 in 0bc8c63

# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s

[jvanasco]

A few lines above suggest the OP is a development shop/agency, and is trying to merge multiple commits and revisions into consolidated changesets for client delivery.

If so, that use-case isn't really supported within any database migration systems I've seen, and really should be done manually. I've managed projects in the past where people have used custom approaches like the one suggested, and it's never a problem until it is - and then it's a big problem that causes a few days of lost work.

[ievgennaida]

Thank you for sharing your experience. I have actually used order by date in the past instead of revisions and it was not so bad.
It can really cause some problems as well that has to be manually managed but at least you don't need to keep sequence manually.