Add 'ExtractTableStorageJob.destination_uri_file_counts' property. (#…

…3803)

bigquery/google/cloud/bigquery/job.py

@@ -1026,6 +1026,22 @@ def __init__(self, name, source, destination_uris, client):
     https://cloud.google.com/bigquery/docs/reference/rest/v2/jobs#configuration.extract.printHeader
     """
 
+    @property
+    def destination_uri_file_counts(self):
+        """Return file counts from job statistics, if present.
+
+        See:
+        https://cloud.google.com/bigquery/docs/reference/rest/v2/jobs#statistics.extract.destinationUriFileCounts
+
+        :rtype: int or None
+        :returns: number of DML rows affectd by the job, or None if job is not
+                  yet complete.
+        """
+        result = self._job_statistics().get('destinationUriFileCounts')
+        if result is not None:
+            result = int(result)
+        return result
+
     def _populate_config_resource(self, configuration):
         """Helper for _build_resource: copy config properties to resource"""
         if self.compression is not None:

bigquery/tests/unit/test_job.py

@@ -1266,6 +1266,23 @@ def test_ctor(self):
         self.assertIsNone(job.field_delimiter)
         self.assertIsNone(job.print_header)
 
+    def test_destination_uri_file_counts(self):
+        file_counts = 23
+        client = _Client(self.PROJECT)
+        source = _Table(self.SOURCE_TABLE)
+        job = self._make_one(self.JOB_NAME, source, [self.DESTINATION_URI],
+                             client)
+        self.assertIsNone(job.destination_uri_file_counts)
+
+        statistics = job._properties['statistics'] = {}
+        self.assertIsNone(job.destination_uri_file_counts)
+
+        extract_stats = statistics['extract'] = {}
+        self.assertIsNone(job.destination_uri_file_counts)
+
+        extract_stats['destinationUriFileCounts'] = str(file_counts)
+        self.assertEqual(job.destination_uri_file_counts, file_counts)
+
     def test_from_api_repr_missing_identity(self):
         self._setUpConstants()
         client = _Client(self.PROJECT)