docs: add clarification around SQL timestamps (#1012)

jackdingilian · web-flow · commit 6e801900bbe9 · 2024-08-08T15:28:11.000-07:00
diff --git a/google/cloud/bigtable/data/execute_query/metadata.py b/google/cloud/bigtable/data/execute_query/metadata.py
@@ -214,6 +214,12 @@ class Bool(Type):
         type_field_name = "bool_type"
 
     class Timestamp(Type):
+        """
+        Timestamp supports :class:`DatetimeWithNanoseconds` but Bigtable SQL does
+        not currently support nanoseconds precision. We support this for potential
+        compatibility in the future. Nanoseconds are currently ignored.
+        """
+
         type_field_name = "timestamp_type"
         expected_types = (
             datetime.datetime,
diff --git a/google/cloud/bigtable/data/execute_query/values.py b/google/cloud/bigtable/data/execute_query/values.py
@@ -100,6 +100,9 @@ def __repr__(self) -> str:
     bool,
     bytes,
     str,
+    # Note that Bigtable SQL does not currently support nanosecond precision,
+    # only microseconds. We use this for compatibility with potential future
+    # support
     DatetimeWithNanoseconds,
     date_pb2.Date,
     "Struct",
