Hi Mike,
thanks a bunch for the quick response!
This is supported by SQLAlchemy more robustly using the
schema_translate_map feature, see
https://docs.sqlalchemy.org/en/13/core/connections.html#schema-translating
. this feature allows schema names to render explicitly without the
need to manipulate search_path.
this feature may not work completely with Alembic however, I'm
evaluating that now.
still doesnt shed any light on your sporadic problem, however.
It's been some time already since I've implemented this, so can't recall
the exact reason why I went down that road but I know for sure that I
was trying to make it work with schema_translate_map but didn't succeed.
I would have very much preferred a solution without patching alembic it
seemed to my last resort at the time. I'd be more than happy to find a
solution here :)
> However, when using that approach you'd normally be running
autogenerate from just one schema, since you are looking to generate
migrations just once and then run them on every tenant.
>
> so it's not clear why autogenerate is being run on every tenant
explicitly - you'd have just one "model" schema that's the one where you
actually run autogenerate upon. there would be no need to consider
other schemas and include_schemas would be set to False.
Indeed that sounds like a good idea. So you'd suggest to keep one schema
just for autogeneration purposes and then apply the migrations to all
customer schemas? Is that possible from within alembic or would you wrap
some tooling around alembic in order to apply migrations one-by-one to
every schema?
> As far as being able to filter out schemas across many, the current
approach is the include_object hook, which is insufficient for many
schemas as it does not block the reflection of all the tables. a new
hook include_name is being added in the coming weeks that allows for
pre-emptive inclusion or exclusion of specific schema names.
I tried the include_object hook back then, but I was facing reflection
issues if I remember correctly. We're using TimescaleDB [1] in the same
database which adds some schemas of its own that alembic doesn't seem to
be able to handle.
> I don't have much insight onto this other than looking at concurrent
activities on the database. "sometimes" usually indicates a race
condition of some sort, and the "autogenerate" process is strictly one
of reading data.
Indeed I'm suspecting the same thing. However, I'm not the most
knowledgable DBA nor do I have an understanding of how alembic actually
compares the current state of the DB with the SA models. Could you maybe
provide a more concrete point what and where to look for?
Thank you for taking the time to help!
Cheers,
Daniel
[1] https://www.timescale.com/
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