Fix get_primary_keys return type

[hab6]

Description

Fix TypeError when querying primary key metadata using reflection.

Related issue #22

Stack dump excerpt and error:

  File "C:\work\.venv\lib\site-packages\sqlalchemy\engine\reflection.py",
        line 1703, in _reflect_pk
    for pk in pk_cons["constrained_columns"]
TypeError: list indices must be integers or slices, not str

Solution

The fix modifies base.py so that the return type from get_primary_keys (wrapped by get_pk_constraint) is now a dictionary (versus a list) and contains the primary key (i.e. constrained column) name.

Note: This solution works with SQLAlchemy version 2.0.27. I was unable to test with SQLAlchemy version 1.4.51 due to an unrelated error that will be addressed in a separate issue.

Testing

Packages and test cases used to verify the fix.

Without the fix, each test case failed with TypeError: list indices must be integers or slices, not str.

With the fix in place, each test case ran successfully.

Versions of selected Python packages used in testing

langchain           0.1.7
langchain-community 0.0.20
langchain-core      0.1.23
langsmith           0.0.87
pyodbc              5.1.0
pypyodbc            1.3.6
setuptools          63.2.0
SQLAlchemy          2.0.27
sqlalchemy-ingres   0.0.5.dev1

Test case 1

test1.py.txt (based on the example in comment)

Test case 2

test2.py.txt (based on the example in comment)

Notable SQLAlchemy related changes

changelog_06.rst - May 16, 2022

Added get_pk_constraint() to reflection.Inspector, similar
to get_primary_keys() except returns a dict that includes the
name of the constraint, for supported backends (PG so far).

changelog_08.rst - Oct 2, 2022

Inspector.get_primary_keys() is
deprecated; use Inspector.get_pk_constraint().

changelog_14.rst - Jan 2, 2024

Remove deprecated method ``get_primary_keys`` in the :class:`.Dialect`
and :class:`_reflection.Inspector` classes. Please refer to the
:meth:`.Dialect.get_pk_constraint`
and :meth:`_reflection.Inspector.get_primary_keys` methods.

Question to consider

Would it be valuable forget_pk_constraint/get_primary_keys to also return the constraint name (in addition to the column name)? I checked the iikeys table of my Actian X 11.2 data database and found these examples of constraint names for defined primary keys: $user__U0000025B0000, $addre_U0000025E0000, $famil_U000002E90000 I don't know whether these constraint names would be at all useful when retrieving primary key metadata.