[GCP] [BigQuery] Handle totalBytesProcessed NoneType

CHANGES.md

@@ -79,6 +79,7 @@
 ## Bugfixes
 
 * Fixed DirectRunner bug in Python SDK where GroupByKey gets empty PCollection and fails when pipeline option `direct_num_workers!=1`. ([#27373](https://github.com/apache/beam/pull/27373))
+* Fixed BigQuery I/O bug when estimating size on queries that utilize row-level security ([#27474](https://github.com/apache/beam/pull/27474))
 
 ## Known Issues
 

sdks/python/apache_beam/io/gcp/bigquery.py

@@ -751,8 +751,17 @@ def estimate_size(self):
           kms_key=self.kms_key,
           job_labels=self._get_bq_metadata().add_additional_bq_job_labels(
               self.bigquery_job_labels))
-      size = int(job.statistics.totalBytesProcessed)
-      return size
+
+      if job.statistics.totalBytesProcessed is None:
+        # Some queries may not have access to `totalBytesProcessed` as a
+        # result of row-level security.
+        # > BigQuery hides sensitive statistics on all queries against
+        # > tables with row-level security.
+        # See cloud.google.com/bigquery/docs/managing-row-level-security
+        # and cloud.google.com/bigquery/docs/best-practices-row-level-security
+        return None
+
+      return int(job.statistics.totalBytesProcessed)
     else:
       # Size estimation is best effort. We return None as we have
       # no access to the query that we're running.
@@ -1102,8 +1111,17 @@ def estimate_size(self):
           kms_key=self.kms_key,
           job_labels=self._get_bq_metadata().add_additional_bq_job_labels(
               self.bigquery_job_labels))
-      size = int(job.statistics.totalBytesProcessed)
-      return size
+
+      if job.statistics.totalBytesProcessed is None:
+        # Some queries may not have access to `totalBytesProcessed` as a
+        # result of row-level security
+        # > BigQuery hides sensitive statistics on all queries against
+        # > tables with row-level security.
+        # See cloud.google.com/bigquery/docs/managing-row-level-security
+        # and cloud.google.com/bigquery/docs/best-practices-row-level-security
+        return None
+
+      return int(job.statistics.totalBytesProcessed)
     else:
       # Size estimation is best effort. We return None as we have
       # no access to the query that we're running.