inspection does not update mapper schema when schema assigned to declarative during runtime

[Peter Lai]

It appears that if during runtime I assign a schema to declarative, then `inspect()` it, the resulting Selectable does not have the schema assigned to it:

in model.py:

from sqlalchemy import Column, String, DateTime
from sqlalchemy.ext.declarative import declarative_base


Base = declarative_base()


class MyClass(Base):
    __tablename__ = 'mytable'


    username = Column(String(128), primary_key=True)

    

in run.py:

from sqlalchemy import create_engine, inspect

from model import MyClass

engine = sqlalchemy.create_engine(...)

MyClass.schema = 'notme'

# I just want to do a manual select on the table not use a session

mytable = inspect(MyClass).local_table

result = engine.execute(mytable.select().first())

#This fails because for the given connection the select table must be qualified under schema 'notme'

#The solution seems to be to assign schema to the Selectable itself, not the declarative:

mytable.schema = 'notme'

Is this an expected behavior?

[Mike Bayer]

yes, there is no significance to an attribute named "schema" on a declarative class.  to set the schema name for a table on the declarative class, __table_args__ must be used as documented at https://docs.sqlalchemy.org/en/13/orm/extensions/declarative/table_config.html?highlight=__table_args__

additionally it's not a good idea to change ".schema" on an already created Table object as the table will be mis-classified within its owning MetaData collection and it will also not work properly with statement caching.

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