RETURNING clause mistakenly added to CREATE and ALTER table statements

[elpete]

When trying to create or alter a table that includes a foreign key constraint and an ON DELETE or ON UPDATE clause, the parser incorrectly marks the CommandType as DELETE or UPDATE, respectively. Combined with a returningColumns of {"*"} (which is the default when just passing in the autoGeneratedKeys flag to execute in PgStatement) this causes a RETURNING clause to be added where it is invalid.

This PR adds four test cases showing the issue.

This PR also adds two new CommandType values for CREATE and ALTER to detect this scenario and prevent the RETURNING clause from being added. This is my first PR to this project and while the tests are passing, there may be a better implementation. I defer to the more seasoned contributors.

I want to add that while using executeUpdate would solve this issue handily, it is unfortunately not exposed by the application framework. They simply use public boolean execute(String sql, int autoGeneratedKeys) and trust this JDBC driver to handle it. I am also working on that project to be more correct in their implementation as well. I think this feature will be a benefit to all regardless of any change in downstream frameworks.

Thank you for your time!

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[davecramer]

I was going to ask how this was possible, since we don't normally see this, but reading the description the project uses execute, instead of executeQuery.