Make sure you have checked _all_ steps below. ### Jira
- [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR" - https://issues.apache.org/jira/browse/AIRFLOW-2997 ### Description - [x] Here are some details about my PR, including screenshots of any UI changes: Bigquery has recently added support for _"clustered"_ tables, which allows the user to request that the result of a query or load operation be stored sorted by one or more columns. This allows subsequent queries to be optimised, and the volume of data queried (and hence cost) potentially reduced when filtering on clustered fields. This PR adds support for clustering to the bigquery hook, bigquery query operator and GCS to bigquery load operator. ### Tests - [x] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason: Tests are added for the run and load operations on the bigquery hook. The operator changes consist of merely passing through a single option to the hook. ### Commits - [x] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)": 1. Subject is separated from body by a blank line 1. Subject is limited to 50 characters (not including Jira issue reference) 1. Subject does not end with a period 1. Subject uses the imperative mood ("add", not "adding") 1. Body wraps at 72 characters 1. Body explains "what" and "why", not "how" ### Documentation - [x] In case of new functionality, my PR adds documentation that describes how to use it. - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added. ### Code Quality - [x] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff` [ Full content available at: https://github.com/apache/incubator-airflow/pull/3838 ] This message was relayed via gitbox.apache.org for [email protected]
