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add mssql_drop_XYZ flags to autogenerate op.drop_column() based on observation of mssql + known type-specific check constraints, defaults, FKs

See original GitHub issue

Migrated issue, originally created by Marek Baczyński (@imbaczek)

DB: SQL Server 2008R2

SQLAlchemy==0.9.3

alembic==0.6.4dev (today’s master and 0.6.3 too)

def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.add_column('table', sa.Column('col1', sa.Enum('one', 'two', name='ck_col1'), nullable=True))
    op.add_column('table', sa.Column('col2', sa.Boolean(name='ck_col2'), nullable=True))
    ### end Alembic commands ###


def downgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.drop_column('table', 'col2')
    op.drop_column('table', 'col1')
    ### end Alembic commands ###

$ alembic downgrade 328
INFO  [alembic.migration] Context impl MSSQLImpl.
INFO  [alembic.migration] Will assume transactional DDL.
INFO  [alembic.migration] Running downgrade 26f5521a70be -> 328b04eddf97, added table table
[...]
  File "pymssql.pyx", line 435, in pymssql.Cursor.execute (pymssql.c:6347)
sqlalchemy.exc.OperationalError: (OperationalError) (5074, "The object 'ck_col2' is dependent on column 'col2'.DB-Lib error message 5074, severity 16:\nGeneral SQL Server error: Check messages from the SQL Server\nDB-Lib error message 4922, severity 16:\nGeneral SQL Server error: Check messages from the SQL Server\n") 'ALTER TABLE [table] DROP COLUMN col2' {}

(constraint names above are tweaked to increase readability, related to #183)

Attachments: 184.patch

Issue Analytics

State:
Created 10 years ago
Comments:17 (1 by maintainers)

Top GitHub Comments

1reaction

sqlalchemy-botcommented, Nov 27, 2018

Michael Bayer (@zzzeek) wrote:

note this refers to all three of: mssql_drop_default, mssql_drop_check, mssql_drop_foreign_key

0reactions

zzzeekcommented, Sep 17, 2019

the related issue is #186 which was fixed.

While it would be nice for this flag to automatically render, this is a fairly special case for now and other than having it render unconditionally in all cases, which would be wasteful, I don’t have a solution right now for how this flag could always come out correctly. If we look into doing a generalized ENUM solution, that would be separate from this.

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