HiveHook fix get_pandas_df() failure when it tries to read an empty table

[iblaine]

closes: #17765

bug fix for get_pandas_df() to avoid an exception when reading an empty table.

---

^ Add meaningful description above

Read the Pull Request Guidelines for more information.
In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in UPDATING.md.

[iblaine]

Do we want to add a new test to test_hive.py? I'm not convinced one is needed because this bug is subtle. And I couldn't figure out how to mock an empty table to trigger this bug.

[uranusjr]

I wonder if it’d work to do SELECT * FROM table LIMIT 0

[iblaine]

I wonder if it’d work to do SELECT * FROM table LIMIT 0

Mock seems to return a result set regardless of the SQL.

[iblaine]

Setting this line to self.iterable = [] will trigger this bug.

[iblaine]

• A new flag empty_table_flag has been added to enable tests against an empty hive table
• A new test has been added to validate get_pandas_df against an empty table

[iblaine]

Test Always API Core Other CLI Providers WWW Integration works locally but is failing here.

[uranusjr]

That transaction failure happens from time to time, likely some sort of race condition in the test runner. We haven't identified the cause yet but it's not related to this change. m

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[iblaine]

We have a few of new failures. These new failures appear to be unrelated to this PR. Should I rebase and try this again, or something else?

• tests/providers/amazon/aws/operators/test_sqs.py - test_execute_success()
• tests/www/test_security.py - test_current_user_has_permissions()

[uranusjr]

The second one is also failing in main and there’s a PR to fix it, so don’t worry about it. I think the first one is already fixed; maybe try rebasing the PR to latest main?

[potiuk]

Only failures that have been fixed recently in main. Merging now to regenerate providers doc.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!