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Unable to compare custom with different data type based on dialect #296

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sqlalchemy-bot opened this Issue Apr 30, 2015 · 6 comments

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sqlalchemy-bot commented Apr 30, 2015

Migrated issue, originally created by Julien Danjou

When using alembic.autogenerate.compare_metadata(), if custom types are used whose implementations differs based on dialect, the comparator generates wrong changes.

For example, when using UUIDType from https://sqlalchemy-utils.readthedocs.org/en/latest/_modules/sqlalchemy_utils/types/uuid.html#UUIDType, the comparator sees this change:

     [ ( 'modify_type',
          None,
          'volume',
          'id',
          { 'existing_nullable': False,
            'existing_server_default': None},
          CHAR(length=32),
          UUIDType(length=16))]]
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sqlalchemy-bot commented Apr 30, 2015

Michael Bayer (@zzzeek) wrote:

  • Added support for type comparison functions to be not just per
    environment, but also present on the custom types themselves, by
    supplying a method compare_against_backend.
    Added a new documentation section :ref:compare_types describing
    type comparison fully.
    fixes #296

dabc7f0

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sqlalchemy-bot commented Apr 30, 2015

Changes by Michael Bayer (@zzzeek):

  • changed status to closed
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sqlalchemy-bot commented Apr 30, 2015

Michael Bayer (@zzzeek) wrote:

thanks for reporting. Note that there is already a publicly documented system of augmenting the type comparison system with your own function, at http://alembic.readthedocs.org/en/latest/api.html#alembic.environment.EnvironmentContext.configure.params.compare_type. However, as this is inconvenient for third party types, support for the compare_against_backend method is also added, as well as a new documentation section.

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sqlalchemy-bot commented Apr 30, 2015

Julien Danjou wrote:

Thanks Mike! 👍

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sqlalchemy-bot commented Apr 30, 2015

Michael Bayer (@zzzeek) wrote:

here's the new section: http://alembic.readthedocs.org/en/latest/autogenerate.html#compare-types. If you can QA the text and the feature itself that would be very helpful

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sqlalchemy-bot commented May 4, 2015

Julien Danjou wrote:

This solves my problem! I just sent you a little typo fix in https://bitbucket.org/zzzeek/alembic/pull-request/44/fix-typo-in-autogenerate-documentation/diff
Thanks again!

@sqlalchemy-bot sqlalchemy-bot added the bug label Nov 27, 2018

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