feat(semantic layers): don't show samples tab in explore

superset-frontend/src/explore/components/DataTablesPane/DataTablesPane.tsx

@@ -197,25 +197,34 @@ export const DataTablesPane = ({
     children: pane,
   }));
 
+  // Hide the Samples tab for datasources that don't expose raw rows
+  // (e.g. semantic views). The check is intentionally ``=== false`` so that
+  // datasources from older backends that don't send the flag still show the
+  // tab and preserve current behavior.
+  const showSamplesTab = datasource?.supports_samples !== false;
   const tabItems = [
     ...queryResultsPanes,
-    {
-      key: ResultTypes.Samples,
-      label: t('Samples'),
-      children: (
-        <StyledDiv>
-          <SamplesPane
-            datasource={datasource}
-            queryFormData={queryFormData}
-            queryForce={queryForce}
-            isRequest={isRequest.samples}
-            setForceQuery={setForceQuery}
-            isVisible={ResultTypes.Samples === activeTabKey}
-            canDownload={canDownload}
-          />
-        </StyledDiv>
-      ),
-    },
+    ...(showSamplesTab
+      ? [
+          {
+            key: ResultTypes.Samples,
+            label: t('Samples'),
+            children: (
+              <StyledDiv>
+                <SamplesPane
+                  datasource={datasource}
+                  queryFormData={queryFormData}
+                  queryForce={queryForce}
+                  isRequest={isRequest.samples}
+                  setForceQuery={setForceQuery}
+                  isVisible={ResultTypes.Samples === activeTabKey}
+                  canDownload={canDownload}
+                />
+              </StyledDiv>
+            ),
+          },
+        ]
+      : []),
   ];
 
   return (

superset-frontend/src/explore/components/DataTablesPane/components/SamplesPane.tsx

@@ -21,6 +21,7 @@ import { t } from '@apache-superset/core/translation';
 import { ensureIsArray } from '@superset-ui/core';
 import { datasetLabelLower } from 'src/features/semanticLayers/label';
 import { styled } from '@apache-superset/core/theme';
+import { Alert } from '@apache-superset/core/components';
 import { EmptyState, Loading } from '@superset-ui/core/components';
 import { GenericDataType } from '@apache-superset/core/common';
 import { GridTable } from 'src/components/GridTable';
@@ -35,7 +36,7 @@ import {
 import { TableControls, ROW_LIMIT_OPTIONS } from './DataTableControls';
 import { SamplesPaneProps } from '../types';
 
-const Error = styled.pre`
+const ErrorAlertWrapper = styled.div`
   margin-top: ${({ theme }) => `${theme.sizeUnit * 4}px`};
 `;
 
@@ -155,7 +156,14 @@ export const SamplesPane = ({
           rowLimitOptions={ROW_LIMIT_OPTIONS}
           onRowLimitChange={handleRowLimitChange}
         />
-        <Error>{responseError}</Error>
+        <ErrorAlertWrapper>
+          <Alert
+            type="error"
+            showIcon
+            message={t('Failed to load samples')}
+            description={responseError}
+          />
+        </ErrorAlertWrapper>
       </>
     );
   }

superset-frontend/src/explore/components/DataTablesPane/components/useResultsPane.tsx

@@ -25,13 +25,14 @@ import {
   getClientErrorObject,
 } from '@superset-ui/core';
 import { styled } from '@apache-superset/core/theme';
+import { Alert } from '@apache-superset/core/components';
 import { EmptyState, Loading } from '@superset-ui/core/components';
 import { getChartDataRequest } from 'src/components/Chart/chartAction';
 import { ResultsPaneProps, QueryResultInterface } from '../types';
 import { SingleQueryResultPane } from './SingleQueryResultPane';
 import { TableControls, ROW_LIMIT_OPTIONS } from './DataTableControls';
 
-const Error = styled.pre`
+const ErrorAlertWrapper = styled.div`
   margin-top: ${({ theme }) => `${theme.sizeUnit * 4}px`};
 `;
 
@@ -157,7 +158,14 @@ export const useResultsPane = ({
           isLoading={false}
           canDownload={canDownload}
         />
-        <Error>{responseError}</Error>
+        <ErrorAlertWrapper>
+          <Alert
+            type="error"
+            showIcon
+            message={t('Failed to load results')}
+            description={responseError}
+          />
+        </ErrorAlertWrapper>
       </>
     );
     return Array(queryCount).fill(err);

superset-frontend/src/explore/components/DataTablesPane/test/DataTablesPane.test.tsx

@@ -89,6 +89,17 @@ describe('DataTablesPane', () => {
     expect(await screen.findByLabelText('Collapse data panel')).toBeVisible();
   });
 
+  test('Hides Samples tab when datasource opts out via supports_samples=false', async () => {
+    const props = createDataTablesPaneProps(0);
+    const propsWithoutSamples = {
+      ...props,
+      datasource: { ...props.datasource, supports_samples: false },
+    };
+    render(<DataTablesPane {...propsWithoutSamples} />, { useRedux: true });
+    expect(await screen.findByText('Results')).toBeVisible();
+    expect(screen.queryByText('Samples')).not.toBeInTheDocument();
+  });
+
   test('Should copy data table content correctly', async () => {
     fetchMock.post(
       'glob:*/api/v1/chart/data?form_data=%7B%22slice_id%22%3A456%7D',

superset-frontend/src/explore/components/DataTablesPane/test/SamplesPane.test.tsx

@@ -84,10 +84,14 @@ describe('SamplesPane', () => {
     const props = createSamplesPaneProps({
       datasourceId: 36,
     });
-    const { findByText } = render(<SamplesPane {...props} />, {
+    const { findByText, findByRole } = render(<SamplesPane {...props} />, {
       useRedux: true,
     });
 
+    // The error is now rendered inside an Alert component, with a clear
+    // headline message and the raw error text as the description.
+    expect(await findByRole('alert')).toBeVisible();
+    expect(await findByText('Failed to load samples')).toBeVisible();
     expect(await findByText('Error: Bad request')).toBeVisible();
   });
 

superset-frontend/src/explore/types.ts

@@ -78,6 +78,12 @@ export type Datasource = Dataset & {
   schema?: string;
   is_sqllab_view?: boolean;
   extra?: string | object;
+  /**
+   * False when the datasource (e.g. a semantic view) doesn't model raw rows
+   * and therefore can't return a row sample. Defaults to true on the server
+   * side; missing here means the explore UI keeps current behavior.
+   */
+  supports_samples?: boolean;
 };
 
 export interface ExplorePageInitialData {

superset/connectors/sqla/models.py

@@ -193,6 +193,11 @@ class BaseDatasource(
     # Only some datasources support Row Level Security
     is_rls_supported: bool = False
 
+    # Datasources that can return raw row samples (anything backed by a SQL
+    # table can; semantic-layer abstractions cannot, since they only expose
+    # pre-defined metrics and dimensions).
+    supports_samples: bool = True
+
     @property
     def name(self) -> str:
         # can be a Column or a property pointing to one
@@ -500,6 +505,7 @@ class BaseDatasource(
             "owners": [owner.id for owner in self.owners],
             "verbose_map": self.verbose_map,
             "select_star": self.select_star,
+            "supports_samples": self.supports_samples,
         }
 
     def data_for_slices(  # pylint: disable=too-many-locals  # noqa: C901

superset/semantic_layers/models.py

@@ -196,6 +196,10 @@ class SemanticView(AuditMixinNullable, Model):
 
     __tablename__ = "semantic_views"
 
+    # Semantic views expose pre-defined metrics and dimensions, not raw rows,
+    # so the "Samples" affordance in Explore does not apply.
+    supports_samples: bool = False
+
     # Use integer as the primary key for cross-database auto-increment
     # compatibility (sa.Identity() is not supported in MySQL or SQLite).
     # The uuid column is a secondary unique identifier used in URLs and perms.
@@ -393,6 +397,7 @@ class SemanticView(AuditMixinNullable, Model):
             "filter_select_enabled": True,
             "sql": None,
             "select_star": None,
+            "supports_samples": self.supports_samples,
             "owners": [],
             "description": self.description,
             "table_name": self.name,

superset/superset_typing.py

@@ -338,6 +338,9 @@ class ExplorableData(TypedDict, total=False):
     extra: str | None
     always_filter_main_dttm: bool
     normalize_columns: bool
+    # Set by datasources that cannot return raw row samples (e.g. semantic
+    # views, which only expose pre-defined metrics and dimensions).
+    supports_samples: bool
 
 
 VizData: TypeAlias = list[Any] | dict[Any, Any] | None

superset/views/datasource/views.py

@@ -208,6 +208,23 @@ class Datasource(BaseSupersetView):
             payload = SamplesPayloadSchema().load(request.json)
         except ValidationError as err:
             return json_error_response(err.messages, status=400)
+
+        # Refuse early for datasource types that don't model raw rows
+        # (e.g. semantic views, which only expose pre-defined metrics and
+        # dimensions). Without this gate the request would still go through
+        # the standard query pipeline and fail with an opaque 500.
+        # ``supports_samples`` defaults to True for any datasource class that
+        # doesn't explicitly opt out, so SqlaTable/Query/SavedQuery continue
+        # to work without needing the attribute declared on each class.
+        ds_class = DatasourceDAO.sources.get(
+            DatasourceType(params["datasource_type"]),
+        )
+        if ds_class is not None and not getattr(ds_class, "supports_samples", True):
+            return json_error_response(
+                _("Samples are not available for this datasource type."),
+                status=400,
+            )
+
         dashboard_id = None
         if security_manager.is_guest_user():
             if not params["dashboard_id"]:

tests/unit_tests/semantic_layers/models_test.py

@@ -653,6 +653,13 @@ def test_semantic_view_data(
         assert data["table_name"] == "Orders View"
         assert data["datasource_name"] == "Orders View"
         assert data["offset"] == 0
+        # Semantic views don't model raw rows, so samples aren't available.
+        assert data["supports_samples"] is False
+
+
+def test_semantic_view_supports_samples_is_false() -> None:
+    """The class-level flag opts SemanticView out of the Samples affordance."""
+    assert SemanticView.supports_samples is False
 
 
 def test_semantic_view_get_query_result(

tests/unit_tests/views/datasource/views_test.py

@@ -312,3 +312,66 @@ def test_save_non_owner_with_owners_field_is_rejected(
             raw_save(_view_self())
 
     mock_security_manager.raise_for_ownership.assert_called_once_with(mock_orm)
+
+
+# ---------------------------------------------------------------------------
+# Datasource.samples
+# ---------------------------------------------------------------------------
+
+
+@patch("superset.views.datasource.views._", lambda s: s)
+@patch("superset.views.datasource.views.get_samples")
+@patch("superset.views.datasource.views.json_error_response")
+@patch("superset.views.datasource.views.security_manager", new_callable=MagicMock)
+def test_samples_returns_400_for_unsupported_datasource_type(
+    mock_security_manager: MagicMock,
+    mock_json_error_response: MagicMock,
+    mock_get_samples: MagicMock,
+) -> None:
+    """Semantic views can't return raw samples — endpoint should refuse with 400."""
+    from flask import Flask
+
+    mock_security_manager.is_guest_user.return_value = False
+    mock_json_error_response.return_value = "error-response"
+
+    raw_samples = _get_view_func("samples")
+    app = Flask(__name__)
+    with app.test_request_context(
+        "/datasource/samples?datasource_type=semantic_view&datasource_id=1",
+        method="POST",
+        json={},
+    ):
+        result = raw_samples(_view_self())
+
+    assert result == "error-response"
+    mock_json_error_response.assert_called_once()
+    _, kwargs = mock_json_error_response.call_args
+    assert kwargs.get("status") == 400
+    # The bail-out must happen before any sample fetching is attempted.
+    mock_get_samples.assert_not_called()
+
+
+@patch("superset.views.datasource.views.get_samples")
+@patch("superset.views.datasource.views.security_manager", new_callable=MagicMock)
+def test_samples_proceeds_for_supported_datasource_type(
+    mock_security_manager: MagicMock,
+    mock_get_samples: MagicMock,
+) -> None:
+    """A `query` datasource (supports_samples=True) bypasses the 400 short-circuit."""
+    from flask import Flask
+
+    mock_security_manager.is_guest_user.return_value = False
+    mock_get_samples.return_value = {"rows": []}
+
+    view = _view_self()
+    raw_samples = _get_view_func("samples")
+    app = Flask(__name__)
+    with app.test_request_context(
+        "/datasource/samples?datasource_type=query&datasource_id=1",
+        method="POST",
+        json={},
+    ):
+        raw_samples(view)
+
+    mock_get_samples.assert_called_once()
+    view.json_response.assert_called_once_with({"result": {"rows": []}})