avoid sample data

weed/query/engine/engine.go

@@ -713,7 +713,8 @@ func (e *SQLEngine) executeSelectStatement(ctx context.Context, stmt *sqlparser.
 	if _, err := e.catalog.GetTableInfo(database, tableName); err != nil {
 		// Topic not in catalog, try to discover and register it
 		if regErr := e.discoverAndRegisterTopic(ctx, database, tableName); regErr != nil {
-			fmt.Printf("Warning: Failed to discover topic %s.%s: %v\n", database, tableName, regErr)
+			// Return error immediately for non-existent topics instead of falling back to sample data
+			return &QueryResult{Error: regErr}, regErr
 		}
 	}
 
@@ -723,14 +724,15 @@ func (e *SQLEngine) executeSelectStatement(ctx context.Context, stmt *sqlparser.
 	var filerClientErr error
 	filerClient, filerClientErr = e.catalog.brokerClient.GetFilerClient()
 	if filerClientErr != nil {
-		// Log warning but continue with sample data fallback
-		fmt.Printf("Warning: Failed to get filer client: %v, using sample data\n", filerClientErr)
+		// Return error if filer client is not available for topic access
+		return &QueryResult{Error: filerClientErr}, filerClientErr
 	}
 
 	hybridScanner, err := NewHybridMessageScanner(filerClient, e.catalog.brokerClient, database, tableName)
 	if err != nil {
-		// Fallback to sample data if topic doesn't exist or filer unavailable
-		return e.executeSelectWithSampleData(ctx, stmt, database, tableName)
+		// Return error for topic access issues instead of misleading sample data
+		topicErr := fmt.Errorf("failed to access topic %s.%s: %v", database, tableName, err)
+		return &QueryResult{Error: topicErr}, topicErr
 	}
 
 	// Parse SELECT columns and detect aggregation functions