On 01/10/2017 06:10 PM, Роберт Шотланд wrote:
Thanks Mike,
Our developers use the ORM exclusively for database access. We maintain
a package containing the tables, relationships, validates, etc.
(*our_db.py*) which is imported in the front-end, back-end modules and
utilities. Recently we added new fields to a table that are calculated
by @validates functions. This "alpha" version of*our_db.p*y-v0.3 depends
on a database that has been migrated to revision id "+2". Then a "beta"
developer working on a database migrated to revision "+1" mistakenly
imports v0.3, (not v0.2) into their venv, it will fail somewhere in the
@validates function probably with 3-pages of indecipherable stack trace.
We'd like to have our_db.py* *catch this error when the database is
opened, perhaps by checking a list of revision id's that are known to be
earlier migrations that are not supported by *our_db-v0.3*.
If you have a list of revision identifiers that are known to be earlier,
you can look up the numbers in the current alembic_version table to see
if they are present, and that would tell you the database is not up to
date, but that means you need to have *all* those revision identifiers
in that list - if one is missing then it might be missed. You'd also
need to devise some way of keeping this list current with each migration
identifier that gets generated - most likely something that happens at
the same time as when you run the "alembic revision" command to create a
new revision file.
Technically, any revision identifier that you read within
alembic_version should be present in this list and you'd know which ones
are the most current - if an identifier in alembic_version is not
present in your list, you'd throw an error - that would likely mean the
database is against a newer version of the code.
If you are using branches in your migrations then there may be more than
one row in alembic_version also (and more than one "head" at a time)
which would make this a multiple-row set operation.
Again, if the actual migration files are locally present in your
application's module base, there's no need to maintain a separate list,
you can construct this "list" from those version files directly using
the ScriptDirectory API.
On Tuesday, January 10, 2017 at 1:02:43 PM UTC-7, Роберт Шотланд wrote:
We have a project in active development that will have periodic
alembic migrations driven by an evolving declarative package. We are
looking for a means of automatically checking (say, at bind-=engine
time?) a list of obsolete alembic revision ids (embedded in our
declarative package), that would throw a custom exception if that
declarative was used with a database that had not been migrated to a
version compatible with that declarative package.
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