fix: access MATERIALIZED_VIEW with read_gbq (#1070)

* fix: corrected inability to access MATERIALIZED_VIEW with read_gbq

* update test

Author: Genesis929

bigframes/core/nodes.py

@@ -547,7 +547,7 @@ class GbqTable:
     table_id: str = field()
     physical_schema: Tuple[bq.SchemaField, ...] = field()
     n_rows: int = field()
-    is_physical_table: bool = field()
+    is_physically_stored: bool = field()
     cluster_cols: typing.Optional[Tuple[str, ...]]
 
     @staticmethod
@@ -563,7 +563,7 @@ def from_table(table: bq.Table, columns: Sequence[str] = ()) -> GbqTable:
             table_id=table.table_id,
             physical_schema=schema,
             n_rows=table.num_rows,
-            is_physical_table=(table.table_type == "TABLE"),
+            is_physically_stored=(table.table_type in ["TABLE", "MATERIALIZED_VIEW"]),
             cluster_cols=None
             if table.clustering_fields is None
             else tuple(table.clustering_fields),
@@ -641,7 +641,7 @@ def variables_introduced(self) -> int:
 
     @property
     def row_count(self) -> typing.Optional[int]:
-        if self.source.sql_predicate is None and self.source.table.is_physical_table:
+        if self.source.sql_predicate is None and self.source.table.is_physically_stored:
             return self.source.table.n_rows
         return None
 

bigframes/session/_io/bigquery/read_gbq_table.py

@@ -102,6 +102,7 @@ def validate_table(
     table_ref: bigquery.table.TableReference,
     columns: Optional[Sequence[str]],
     snapshot_time: datetime.datetime,
+    table_type: str,
     filter_str: Optional[str] = None,
 ) -> bool:
     """Validates that the table can be read, returns True iff snapshot is supported."""
@@ -124,6 +125,17 @@ def validate_table(
     if table_ref.dataset_id.startswith("_"):
         return False
 
+    # Materialized views，does not support snapshot
+    if table_type == "MATERIALIZED_VIEW":
+        warnings.warn(
+            "Materialized views do not support FOR SYSTEM_TIME AS OF queries. "
+            "Attempting query without time travel. Be aware that as materialized views "
+            "are updated periodically, modifications to the underlying data in the view may "
+            "result in errors or unexpected behavior.",
+            category=bigframes.exceptions.TimeTravelDisabledWarning,
+        )
+        return False
+
     # Second, try with snapshot to verify table supports this feature
     snapshot_sql = bigframes.session._io.bigquery.to_query(
         query_or_table=f"{table_ref.project}.{table_ref.dataset_id}.{table_ref.table_id}",

bigframes/session/loader.py

@@ -339,7 +339,12 @@ def read_gbq_table(
         )
 
         enable_snapshot = enable_snapshot and bf_read_gbq_table.validate_table(
-            self._bqclient, table_ref, all_columns, time_travel_timestamp, filter_str
+            self._bqclient,
+            table_ref,
+            all_columns,
+            time_travel_timestamp,
+            table.table_type,
+            filter_str,
         )
 
         # ----------------------------

tests/system/small/test_dataframe.py

@@ -1524,6 +1524,10 @@ def test_shape(scalars_dfs):
 @pytest.mark.parametrize(
     "reference_table, test_table",
     [
+        (
+            "bigframes-dev.bigframes_tests_sys.base_table",
+            "bigframes-dev.bigframes_tests_sys.base_table_mat_view",
+        ),
         (
             "bigframes-dev.bigframes_tests_sys.base_table",
             "bigframes-dev.bigframes_tests_sys.base_table_view",

tests/system/small/test_session.py

@@ -390,9 +390,16 @@ def test_read_gbq_twice_with_same_timestamp(session, penguins_table_id):
     assert df3 is not None
 
 
-def test_read_gbq_on_linked_dataset_warns(session):
+@pytest.mark.parametrize(
+    "source_table",
+    [
+        "bigframes-dev.thelook_ecommerce.orders",
+        "bigframes-dev.bigframes_tests_sys.base_table_mat_view",
+    ],
+)
+def test_read_gbq_on_linked_dataset_warns(session, source_table):
     with warnings.catch_warnings(record=True) as warned:
-        session.read_gbq("bigframes-dev.thelook_ecommerce.orders")
+        session.read_gbq(source_table)
         assert len(warned) == 1
         assert warned[0].category == bigframes.exceptions.TimeTravelDisabledWarning