Variant base not taken into account when comparing types

[sqlalchemy-bot]

Migrated issue, originally created by Dheeraj Gupta

I have a set of migration tests for my model which has a lot of autoincrement primary keys not all of which are Integer.

To support sqlite, my models have id lines like so

id_ = Column("id", BigInteger().with_variant(Integer, "sqlite"),
                 primary_key=True)

I use alembic for migrations and have written tests which compare the types of columns too. For versions of alembic <= 0.8.3, all tests pass. However, for versions newer than 0.8.4, I get the following differences from metadata (leading to test failure)

[('modify_type', None, 'ip_checkpoint', 'id', {'existing_server_default': False, 'existing_nullable': None}, BIGINT(display_width=20), Variant())]

I understand that Issue 341 had added additional type comparison and this change probably broke my tests.

Is it possible to fine-tune type checking for variants or should I just rework my tests to ignore such differences?

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

seeing that failure against SQLite or against other backends? current observation is the SQLite comparison will succeed because it compares only Integer. There seems to be a problem with the BigInteger() part of it, however, e.g. on other backends.

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• removed labels: low priority

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed title from "Alembic upgrade from 0.8.3 to 0.8.4 or later break" to "Variant base not taken into account when comparing"

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• set milestone to "fasttrack"

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

even though we do dialect_impl() in the comparison, apparently for Variant if you are on a default dialect it gives you back itself (because it's a TypeDecorator). need to adjust for this.

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

https://gerrit.sqlalchemy.org/420

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Adjust for Variant returning itself as impl

Fixed bug where autogen comparison of a :class:.Variant datatype
would not compare to the dialect level type for the "default"
implementation of the :class:.Variant, returning the type as changed
between database and table metadata.

Change-Id: Ie94779ece9f1c768375cdbdc4124c98f9c11bb86
Fixes: #433

→ 54c5abb

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed status to closed

[sqlalchemy-bot]

Dheeraj Gupta wrote:

@zzzeek Yes you are correct....tests succeed for SQLite backend but fail for MySQL backend.

Thanks for the quick-fix.