Per the title.
Resolved in release 1.2.0-incubating (2015-04-16)
Fixed in http://git-wip-us.apache.org/repos/asf/incubator-calcite/commit/4d2f647a.
Your version of the patch (still) works for me!
I've fixed the NPE. If the JSON result doesn't contain columns, Avatica now makes up the definitions by inspecting the fields of the metadata class, e.g. MetaTable.class.
New patch adds a test. It's throwing NPE, which I don't see when running the code with my real client/server. Seems like Something in the test stack is putting a null for a Signature. Mind having a look?
Needs a test.