On 05/31/2017 08:51 AM, Amrith Kumar wrote:
This email thread relates to[1], a change that aims to improve cross-SQL
support in project schemas.
I want to explicitly exclude the notion of getting rid of support for
PostgreSQL in the underlying project schemas, a topic that was discussed
at the summit[2].
In this change, the author (Thomas Bechtold, copied on this thread)
makes the comment that the change "is not changing the schema. It just
avoids implicit type conversion".
It has long been my understanding that changes like this are not upgrade
friendly as it could lead to two installations both with, say version 37
or 38 of the schema, but different table structures. In effect, this
change breaks upgradability of systems.
i.e. a deployment which had a schema from the install of Ocata would
have a v38 table modules table with a default of 0 and one installed
with Pike (should this change be accepted) would have a modules table
with a default of False.
I agree that if that was the case this would be bad. But I don't think
it's the case here.
The datatype in the model is already Boolean. So I believe that means
this will be a tinyint in MySQL and likely a boolean in PG (I'm
guessing) the only change here is to the SQLA layer in what is being
used in code - and being more explicit seems good.
So I think this is a win.
I'm raising this issue on the ML because the author also claims (albeit
not verified by me) that other projects have accepted changes like this.
Thanks! I think this is an area we need to be careful in - and extra
eyeballs are a good thing.
I submit to you that the upgrade friendly way of making this change
would be to propose a new version of the schema which alters all of
these tables and includes the correct default value. On a fresh install,
with no data, the upgrade step with this new schema version would bring
the table to the right default value and any system with that version of
the schema would have an identical set of defaults. Similarly any system
with v37 or 38 of the schema would have identical defaults.
Yes - I agree - that would definitely be the right way to do this if
there was a model change.
What's the advice of the community on this change; I've explicitly added
stable-maint-core as reviewers on this change as it does have stable
branch upgrade implications.
-amrith
[1] https://review.openstack.org/#/c/467080/
[2]https://etherpad.openstack.org/p/BOS-postgresql
--
Amrith Kumar
Phone: +1-978-563-9590
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