add dataset type selection test and fix bug in tests

dlt/destinations/dataset/dataset.py

@@ -115,6 +115,7 @@ def __call__(self, query: Any) -> ReadableDBAPIRelation:
 
     def table(self, table_name: str) -> SupportsReadableRelation:
         # we can create an ibis powered relation if ibis is available
+        print(table_name in self.schema.tables, self._dataset_type)
         if table_name in self.schema.tables and self._dataset_type in ("auto", "ibis"):
             try:
                 from dlt.common.libs.ibis import create_unbound_ibis_table

tests/load/test_read_interfaces.py

@@ -155,6 +155,24 @@ def double_items():
 )
 
 
+@pytest.mark.no_load
+@pytest.mark.essential
+@pytest.mark.parametrize(
+    "populated_pipeline",
+    configs,
+    indirect=True,
+    ids=lambda x: x.name,
+)
+def test_explicit_dataset_type_selection(populated_pipeline: Pipeline):
+    from dlt.destinations.dataset.dataset import ReadableDBAPIRelation
+    from dlt.destinations.dataset.ibis_relation import ReadableIbisRelation
+
+    assert isinstance(
+        populated_pipeline._dataset(dataset_type="default").items, ReadableDBAPIRelation
+    )
+    assert isinstance(populated_pipeline._dataset(dataset_type="ibis").items, ReadableIbisRelation)
+
+
 @pytest.mark.no_load
 @pytest.mark.essential
 @pytest.mark.parametrize(
@@ -272,7 +290,7 @@ def test_db_cursor_access(populated_pipeline: Pipeline) -> None:
 )
 def test_hint_preservation(populated_pipeline: Pipeline) -> None:
     # NOTE: for now hints are only preserved for the default dataset
-    table_relationship = populated_pipeline._dataset("default").items
+    table_relationship = populated_pipeline._dataset(dataset_type="default").items
     # check that hints are carried over to arrow table
     expected_decimal_precision = 10
     expected_decimal_precision_2 = 12
@@ -365,7 +383,7 @@ def test_limit_and_head(populated_pipeline: Pipeline) -> None:
     ids=lambda x: x.name,
 )
 def test_column_selection(populated_pipeline: Pipeline) -> None:
-    table_relationship = populated_pipeline._dataset("default").items
+    table_relationship = populated_pipeline._dataset(dataset_type="default").items
     columns = ["_dlt_load_id", "other_decimal"]
     data_frame = table_relationship.select(*columns).head().df()
     assert [v.lower() for v in data_frame.columns.values] == columns