Fix validation for BQ label values for BigQueryInsertJobOperator

[kisssam]

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This updates the label value validation logic for BigQuery label values as documented in the public documentation

closes: #39567

[boring-cyborg]

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[kisssam]

Setting the regex as LABEL_REGEX = re.compile(r"^[\w-]{0,63}$") since the documentation [1] indicates that label values can start with numbers, hyphen and underscore as well.

Values can be empty, and have a maximum length of 63 characters.

... values can contain only lowercase letters, numeric characters, underscores, and dashes

[1] https://cloud.google.com/bigquery/docs/labels-intro#requirements

[shahar1]

Setting the regex as LABEL_REGEX = re.compile(r"^[\w-]{0,63}$") since the documentation [1] indicates that label values can start with numbers, hyphen and underscore as well.

Values can be empty, and have a maximum length of 63 characters.

... values can contain only lowercase letters, numeric characters, underscores, and dashes

[1] https://cloud.google.com/bigquery/docs/labels-intro#requirements

What about Keys must start with a lowercase letter or international character.?

[kisssam]

Setting the regex as LABEL_REGEX = re.compile(r"^[\w-]{0,63}$") since the documentation [1] indicates that label values can start with numbers, hyphen and underscore as well.

Values can be empty, and have a maximum length of 63 characters.

... values can contain only lowercase letters, numeric characters, underscores, and dashes

[1] https://cloud.google.com/bigquery/docs/labels-intro#requirements

What about Keys must start with a lowercase letter or international character.?

As mentioned in this line, as part of the label addition logic, the label keys used will be static, i.e. airflow-dag and airflow-task - hence the validation is only needed for the label values being passed, which the above validation regex will take care of.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[kisssam]

On testing on a Cloud Composer environment with apache-airflow-providers-google==10.18.0rc2, all other test cases except the scenario where a task starts with a hyphen fails.

However, this appears to be because Airflow DAG names and task IDs do not work well if they start with hyphen as seen in the below example:

However, I can confirm as seen below for a example BigQuery job that I created that BigQuery labels support labels starting with hyphens as mentioned above.

But the BigQueryInsertJobOperator would not be able to create jobs with label values starting with hyphen since it appears that task IDs cannot start with hyphens.

Hence, can you please let me know if this makes sense to remove the test case for the task starting with a hyphen since although Airflow allows to create a DAG/task starting with hyphen, it is not going to work as expected ? @eladkal