Document retry of exceptions while streaming 'read'/'execute_sql' results

docs/spanner/snapshot-usage.rst

@@ -64,9 +64,24 @@ fails if the result set is too large,
 
 .. note::
 
-   If streaming a chunk fails due to a "resumable" error,
-   :meth:`Session.read` retries the ``StreamingRead`` API reqeust,
-   passing the ``resume_token`` from the last partial result streamed.
+   If streaming a chunk raises an exception, the application can
+   retry the ``read``, passing the ``resume_token`` from ``StreamingResultSet``
+   which raised the error.  E.g.:
+
+   .. code:: python
+
+      result = snapshot.read(table, columns, keys)
+      while True:
+          try:
+              for row in result.rows:
+                  print row
+          except Exception:
+               result = snapshot.read(
+                  table, columns, keys, resume_token=result.resume_token)
+               continue
+          else:
+              break
+
 
 
 Execute a SQL Select Statement
@@ -97,6 +112,26 @@ fails if the result set is too large,
    manually, perform all iteration within the context of  the
    ``with database.snapshot()`` block.
 
+.. note::
+
+   If streaming a chunk raises an exception, the application can
+   retry the query, passing the ``resume_token`` from ``StreamingResultSet``
+   which raised the error.  E.g.:
+
+   .. code:: python
+
+      result = snapshot.execute_sql(QUERY)
+      while True:
+          try:
+              for row in result.rows:
+                  print row
+          except Exception:
+               result = snapshot.execute_sql(
+                  QUERY, resume_token=result.resume_token)
+               continue
+          else:
+              break
+
 
 Next Step
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