Fix: ensure get_df uses SQLAlchemy engine to avoid pandas warning

[daesung9511]

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Fix PostgresHook.get_df() warning when using non-SQLAlchemy connections

This PR updates the PostgresHook.get_df() implementation to avoid triggering a UserWarning from pandas when the underlying connection is not an instance of sqlalchemy.engine.Connection. The patch ensures better compatibility with non-SQLAlchemy connections and avoids log clutter during DAG execution.

This change only affects the Postgres provider and does not alter the interface or behavior for existing users using SQLAlchemy-compatible connections.

closes: #52142

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[bugraoz93]

Thanks a lot for your PR! Could you please also include unit tests?

[bugraoz93]

Thanks for the updates!

[daesung9511]

Hi, just a kind reminder for the review. I’m here and ready to hear your advice and revise the code. Thanks!
@bugraoz93

[potiuk]

Nice!

[potiuk]

Let's see if CI agrees :)

[bugraoz93]

Hi, just a kind reminder for the review. I’m here and ready to hear your advice and revise the code. Thanks!
@bugraoz93

Thanks for the changes!

[bugraoz93]

I think CI needs some love on tests :)

[daesung9511]

Hi, I modified the pyproject.toml and rolled back the code to ensure it passes with the minimal required dependencies and aligns the method signature with its superclass, as required by mypy in the unit tests.
Please let me know if anything should be further modified or removed. Otherwise, it looks like the CI has passed.
Thanks again for your time and review! @bugraoz93 @potiuk

It passed in the previous commit (133408b).

[bugraoz93]

Thanks a lot @daesung9511! Could you please rebase the branch for a cleaner commit history? I believe it is always merged with the incoming changes. I think we can merge it afterwards. Great work!