I'm using postgres version 10, alembic 1.0.0, sqlalchemy 1.2.12. I'm aware
ALTER COLUMN in SQL doesn't delete rows, but op.alter_column is doing that.
My customer & daily reading models look like:
class Customer(DeclarativeBase):
__tablename__ = 'customers'
id = Column(Integer, primary_key=True)
electricity_readings = relationship(
'ElectricityMeterReading', cascade='all,delete-orphan',
backref=backref('customer', cascade='all')
)
gas_readings = relationship(
'GasMeterReading', cascade='all,delete-orphan',
backref=backref('customer', cascade='all')
)
daily_smart_meter_readings = relationship(
'DailyMeterReading',
cascade='all,delete-orphan',
backref=backref('customer', cascade='all')
)
class DailyMeterReading(DeclarativeBase):
__tablename__ = 'daily_smart_meter_readings'
id = Column(Integer, primary_key=True)
customer_pk = Column(
Integer, ForeignKey('customers.id'), nullable=False, index=True
)
reading = Column(Float, nullable=False)
reading_at = Column(UtcDateTime, nullable=False, index=True)
On Monday, October 8, 2018 at 3:26:11 PM UTC+1, Mike Bayer wrote:
>
> Hi there -
>
> I have no idea what you are seeing. an actual ALTER COLUMN
> operation does not delete rows. Of course, if you are using SQLite
> and batch mode, that might affect things, but you have not specified
> this. Please specify complete information including log output,
> stack traces, database in use, sample schema, etc.
>
> On Mon, Oct 8, 2018 at 9:36 AM Richard <goo...@richard.do> wrote:
> >
> >
> > Note that if I do the same op.alter_column on another table which has a
> customer FK, it works fine and does not delete all the rows.
> >
> > On Monday, October 8, 2018 at 1:50:38 PM UTC+1, Richard wrote:
> >>
> >> I have an alembic migration which renames a FK column on a table from
> 'customer_id' to 'customer_pk'.
> >>
> >> I used to have more in the migration file but narrowed it down to this
> code causing all the rows to be deleted.
> >>
> >> def upgrade():
> >> op.alter_column(
> >> 'daily_smart_meter_readings', column_name='customer_id',
> >> new_column_name='customer_pk',
> >> )
> >>
> >>
> >> I'm using alembic==1.0.0 and Python 3.6.4.
> >>
> >> Is there something wrong with the above code or is this a bug in the
> library?
> >>
> >> Thanks
> >
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