Add 'QueryJob.results' factory.

Constructs a 'QueryResults' instance, bound to the job.

Closes #2083.

Author: tseaver

google/cloud/bigquery/job.py

@@ -1073,3 +1073,12 @@ def from_api_repr(cls, resource, client):
         job = cls(name, query, client=client)
         job._set_properties(resource)
         return job
+
+    def results(self):
+        """Construct a QueryResults instance, bound to this job.
+
+        :rtype: :class:`~google.cloud.bigquery.query.QueryResults`
+        :returns: results instance
+        """
+        from google.cloud.bigquery.query import QueryResults
+        return QueryResults.from_query_job(self)

unit_tests/bigquery/test_job.py

@@ -1386,6 +1386,14 @@ def test_from_api_repr_w_properties(self):
         self.assertTrue(dataset._client is client)
         self._verifyResourceProperties(dataset, RESOURCE)
 
+    def test_results(self):
+        from google.cloud.bigquery.query import QueryResults
+        client = _Client(self.PROJECT)
+        job = self._makeOne(self.JOB_NAME, self.QUERY, client)
+        results = job.results()
+        self.assertIsInstance(results, QueryResults)
+        self.assertTrue(results._job is job)
+
     def test_begin_w_bound_client(self):
         PATH = 'projects/%s/jobs' % self.PROJECT
         RESOURCE = self._makeResource()