Re: alembic upgrade not idempotent?

[bertrand]

Sorry for the confusion, I meant "alembic upgrade head" indeed.  As you 
confirmed the expected behavior, I did a bit of debugging to find out where 
I might have done a mistake, and I found the problem.

I wrote a test revision that looked like the following:

def upgrade():
bind = op.get_bind()
db = Session(bind)
db.execute('alter table cats rename to dogs') 

With level = DEBUG for [logger_sqlalchemy], I get:

> alembic upgrade head
INFO  [sqlalchemy.engine.base.Engine] SELECT CAST('test plain returns' AS 
VARCHAR(60)) AS anon_1
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] SELECT CAST('test unicode returns' AS 
VARCHAR(60)) AS anon_1
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [sqlalchemy.engine.base.Engine] PRAGMA table_info("alembic_version")
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] PRAGMA table_info("alembic_version")
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] 
CREATE TABLE alembic_version (
version_num VARCHAR(32) NOT NULL
)


INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] COMMIT
INFO  [alembic.runtime.migration] Running upgrade  -> 80def0e180bc, Rename 
cats to dogs
INFO  [sqlalchemy.engine.base.Engine] BEGIN (implicit)
INFO  [sqlalchemy.engine.base.Engine] alter table cats rename to dogs
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] INSERT INTO alembic_version (
version_num) VALUES ('80def0e180bc')
INFO  [sqlalchemy.engine.base.Engine] ()
INFO  [sqlalchemy.engine.base.Engine] ROLLBACK

As you can see, my omission of db.commit() caused alembic's version upgrade 
to be rolled back.  However, the table has really been renamed from "cats" 
to "dogs".  Therefore, a second run of alembic upgrade head will fail in 
this case.

-- 
You received this message because you are subscribed to the Google Groups 
"sqlalchemy-alembic" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to sqlalchemy-alembic+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Re: alembic upgrade not idempotent?

[Mike Bayer]

On 04/18/2016 10:56 AM, bertr...@cryptosense.com wrote:

Hi,

Here's something quite fundamental I don't understand about alembic.
I've initialized my database and created a revision meant to be executed
online.  I went like this:
|
alembic init app/alembic
# edit configuration
alembic revision -m 'Data modification'
# edit revision script
alembic upgrade
|

If I run alembic upgrade a second time, it runs the upgradefunction
again, which results in an error because my function should not be run
on the new database (it's not idempotent). Why doesn't alembic figure
out that the upgrade has already been applied? This is especially
annoying in production where I just want to make sure the database is up
to date without having to guess which revision script to execute.


I'm not understanding what you are actually doing.  It is an error to 
run "alembic upgrade" without a target:


$ alembic upgrade
usage: alembic upgrade [-h] [--sql] [--tag TAG] revision
alembic upgrade: error: too few arguments


When you specify a target, say "head", it updates the version table:

$ .venv/bin/alembic upgrade head
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> e12f6fb70dcc, rev 1

and then the next time, it will do nothing:

$ .venv/bin/alembic upgrade head
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.


so it appears like you have some entirely customized setup going on, 
which itself would be where your issue lies.










Best,

--
Bertrand

--
You received this message because you are subscribed to the Google
Groups "sqlalchemy-alembic" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to sqlalchemy-alembic+unsubscr...@googlegroups.com
.
For more options, visit https://groups.google.com/d/optout.


--
You received this message because you are subscribed to the Google Groups 
"sqlalchemy-alembic" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to sqlalchemy-alembic+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.