Dev-iL commented on code in PR #55954:
URL: https://github.com/apache/airflow/pull/55954#discussion_r2382719028
##########
airflow-core/src/airflow/models/backfill.py:
##########
@@ -39,7 +38,18 @@
select,
)
from sqlalchemy.exc import IntegrityError
-from sqlalchemy.orm import relationship, validates
+
+try:
+ from sqlalchemy.orm import mapped_column
+except ImportError:
+ # fallback for SQLAlchemy < 2.0
+ def mapped_column(*args, **kwargs):
+ from sqlalchemy import Column
+
+ return Column(*args, **kwargs)
Review Comment:
I agree with Ash's comment - that was, after all, the purpose of the shim
suggested by the LLM. However, I also see your point. Just to clarify, the
alternative is:
```python
"""
Shim for dual SQLAlchemy 1.4 / 2.0 support.
# Why this works?
* On 1.4: MyPy "sees" Mapped/mapped_column via stubs, so model attributes
resolve to instance types (str, int, datetime, …) instead of Column[...].
* At runtime on 1.4: mapped_column falls back to Column, so models still
construct.
* On 2.0: Native imports are used; the shim becomes a thin pass-through.
# Eventual removal of 1.4 support:
Delete the below and replace imports with `from sqlalchemy.orm import
Mapped, mapped_column`.
"""
# ruff: noqa: F401
from __future__ import annotations
TYPE_CHECKING: bool = False
if TYPE_CHECKING:
# For type-checkers, use real 2.0 types (via sqlalchemy2-stubs on 1.4)
from sqlalchemy import Select
from sqlalchemy.orm import Mapped, Session, mapped_column
else:
# At runtime, import what exists; gracefully fall back on 1.4
try: # SA 1.4+ often exposes these names; SA 2.0 surely does
from sqlalchemy.orm import Mapped, Session, mapped_column # type:
ignore
except Exception:
from typing import Any as Mapped # runtime only; type-checkers hit
the branch above
from sqlalchemy import Column as mapped_column # maps to 1.4
Column()
try:
from sqlalchemy import Select # SA 2.0
except Exception: # 1.4
from sqlalchemy.sql import Select # type: ignore
```
Then in the models it's as simple as:
```python
from airflow.utils.sqlalchemy import Mapped, Session, mapped_column
```
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