hi there -
would need a complete example and SQLAlchemy version in use, Table does have a
"_columns" attribute and both patterns described below are things that should
work without an error like this, additionally the complete stack trace would
also be helpful. Unpickling the metadata is a place where it is more
plausible that the state of the Table is broken but that does not apply when
you are just doing autoload_with.
On Thu, Mar 25, 2021, at 1:33 PM, Demitri Muna wrote:
> Hello,
>
> I’m working on migrating my existing code to the updated APIs. My class
> definitions for tables before looked like this:
>
> class MyTable(Base):
> __tablename__ = ‘my_table’
> __table_args__ = {'autoload' : True, 'schema' : ‘my_schema’}
>
> I’m trying to implement declarative mapping via reflected tables, as
> described here:
> https://docs.sqlalchemy.org/en/14/orm/declarative_tables.html#mapping-declaratively-with-reflected-tables
>
> This is my new code:
>
> engine = create_engine(“postgresql:…")
> metadata = MetaData()
> metadata.reflect(bind=dbc.engine, schema='my_schema’)
>
> class MyTable(Base):
> __table__ = Table(name=‘my_table', schema=‘my_schema',
> metadata=metadata, autoload_with=engine)
>
> This is the (truncated) error I’m getting:
>
> AttributeError: 'Table' object has no attribute '_columns'
> > /usr/custom/anaconda/lib/python3.7/site-packages/sqlalchemy/sql/selectable.py(747)columns()
> 745 self._init_collections()
> 746 self._populate_column_collection()
> --> 747 return self._columns.as_immutable()
> 748
> 749 @property
>
> Is there more that’s needed to be done to define the class? I can create a
> MWE, but thought I’d check to see if I’m missing something new.
>
> Related to this, I currently pickle my metadata to reuse since the schema
> changes infrequently. When I have this, I use:
>
> metadata = <load from pickle>
>
> class MyTable(Base):
> __table__ = metadata.tables[‘my_schema.my_table’]
>
> Will this still work? Although from what I read from the docs, I wondered if
> I can use the Table(…) line above unchanged in this case as Metadata won’t go
> to the server if the 'schema.table’ is in the class?
>
> Cheers,
> Demitri
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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