test: check extreme DATE/DATETIME values can be loaded from pandas DataFrame (googleapis#1078)

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Towards #1076 🦕
(edit: moved to googleapis/python-db-dtypes-pandas#45 )

Author: tswast

tests/system/test_pandas.py

@@ -268,7 +268,7 @@ def test_load_table_from_dataframe_w_nulls(bigquery_client, dataset_id):
     See: https://github.com/googleapis/google-cloud-python/issues/7370
     """
     # Schema with all scalar types.
-    scalars_schema = (
+    table_schema = (
         bigquery.SchemaField("bool_col", "BOOLEAN"),
         bigquery.SchemaField("bytes_col", "BYTES"),
         bigquery.SchemaField("date_col", "DATE"),
@@ -283,15 +283,6 @@ def test_load_table_from_dataframe_w_nulls(bigquery_client, dataset_id):
         bigquery.SchemaField("ts_col", "TIMESTAMP"),
     )
 
-    table_schema = scalars_schema + (
-        # TODO: Array columns can't be read due to NULLABLE versus REPEATED
-        #       mode mismatch. See:
-        #       https://issuetracker.google.com/133415569#comment3
-        # bigquery.SchemaField("array_col", "INTEGER", mode="REPEATED"),
-        # TODO: Support writing StructArrays to Parquet. See:
-        #       https://jira.apache.org/jira/browse/ARROW-2587
-        # bigquery.SchemaField("struct_col", "RECORD", fields=scalars_schema),
-    )
     num_rows = 100
     nulls = [None] * num_rows
     df_data = [
@@ -372,7 +363,8 @@ def test_load_table_from_dataframe_w_explicit_schema(bigquery_client, dataset_id
     # See:
     #       https://github.com/googleapis/python-bigquery/issues/61
     #       https://issuetracker.google.com/issues/151765076
-    scalars_schema = (
+    table_schema = (
+        bigquery.SchemaField("row_num", "INTEGER"),
         bigquery.SchemaField("bool_col", "BOOLEAN"),
         bigquery.SchemaField("bytes_col", "BYTES"),
         bigquery.SchemaField("date_col", "DATE"),
@@ -387,17 +379,8 @@ def test_load_table_from_dataframe_w_explicit_schema(bigquery_client, dataset_id
         bigquery.SchemaField("ts_col", "TIMESTAMP"),
     )
 
-    table_schema = scalars_schema + (
-        # TODO: Array columns can't be read due to NULLABLE versus REPEATED
-        #       mode mismatch. See:
-        #       https://issuetracker.google.com/133415569#comment3
-        # bigquery.SchemaField("array_col", "INTEGER", mode="REPEATED"),
-        # TODO: Support writing StructArrays to Parquet. See:
-        #       https://jira.apache.org/jira/browse/ARROW-2587
-        # bigquery.SchemaField("struct_col", "RECORD", fields=scalars_schema),
-    )
-
     df_data = [
+        ("row_num", [1, 2, 3]),
         ("bool_col", [True, None, False]),
         ("bytes_col", [b"abc", None, b"def"]),
         ("date_col", [datetime.date(1, 1, 1), None, datetime.date(9999, 12, 31)]),
@@ -464,6 +447,22 @@ def test_load_table_from_dataframe_w_explicit_schema(bigquery_client, dataset_id
     assert tuple(table.schema) == table_schema
     assert table.num_rows == 3
 
+    result = bigquery_client.list_rows(table).to_dataframe()
+    result.sort_values("row_num", inplace=True)
+
+    # Check that extreme DATE/DATETIME values are loaded correctly.
+    # https://github.com/googleapis/python-bigquery/issues/1076
+    assert result["date_col"][0] == datetime.date(1, 1, 1)
+    assert result["date_col"][2] == datetime.date(9999, 12, 31)
+    assert result["dt_col"][0] == datetime.datetime(1, 1, 1, 0, 0, 0)
+    assert result["dt_col"][2] == datetime.datetime(9999, 12, 31, 23, 59, 59, 999999)
+    assert result["ts_col"][0] == datetime.datetime(
+        1, 1, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
+    )
+    assert result["ts_col"][2] == datetime.datetime(
+        9999, 12, 31, 23, 59, 59, 999999, tzinfo=datetime.timezone.utc
+    )
+
 
 def test_load_table_from_dataframe_w_struct_datatype(bigquery_client, dataset_id):
     """Test that a DataFrame with struct datatype can be uploaded if a