[Sqlalchemy-tickets] Issue #4234: Foreign key constraints not reflected from SQL Server Database (zzzeek/sqlalchemy)

[Dave H. <iss...@bi...>]

New issue 4234: Foreign key constraints not reflected from SQL Server Database
https://bitbucket.org/zzzeek/sqlalchemy/issues/4234/foreign-key-constraints-not-reflected-from

Dave Hirschfeld:

Assuming a SQL Server database with two schemas `TEST1` and `TEST2` the below MVCE demonstrates that the foreign key constraint isn't correctly reflected from the database:
```python
import sqlalchemy as sa

engine = sa.create_engine(
    f"mssql://{server}/{database}?driver=ODBC+Driver+13+for+SQL+Server"
)

metadata = sa.MetaData()

table1 = sa.Table(
    'TrueFalse', metadata,
    sa.Column('id', sa.SmallInteger, primary_key=True),
    sa.Column('name', sa.String(5), nullable=False),
    schema='TEST2',
)

table2 = sa.Table(
    'TestTable', metadata,
    sa.Column('id', sa.Integer, primary_key=True),
    sa.Column('true_false', sa.SmallInteger, sa.ForeignKey(table1.c.id)),
    schema='TEST1',
)

metadata.create_all(engine)

table3 = sa.Table('TestTable', sa.MetaData(bind=engine), schema='TEST1', autoload=True)
```
```python
In [10]: table2.foreign_keys
Out[10]: {ForeignKey('TEST2.TrueFalse.id')}

In [11]: table3.foreign_keys
Out[11]: set()          <---------- SHOULD BE THE SAME AS TABLE2!!!
```
The FK constraint is created correctly in the database.