Sanitize generated DSL and update execution flow in search handler

- Introduce a new sanitizeDSL function to clean up unsupported wildcards in the generated DSL.
- Adjust the sequence of operations in SearchWithContext to reflect the new sanitization step.
- Update comments to accurately reflect the changes in the execution flow and improve code clarity.

agent/search/handlers/db/handler.go

@@ -164,10 +164,13 @@ func (h *Handler) SearchWithContext(ctx *agentContext.Context, req *types.Reques
 		}, nil
 	}
 
-	// 3. Merge preset conditions into generated DSL
+	// 3. Sanitize generated DSL (remove unsupported wildcards like "*")
+	h.sanitizeDSL(result.DSL)
+
+	// 4. Merge preset conditions into generated DSL
 	h.mergeDSLConditions(result.DSL, req)
 
-	// 4. Execute QueryDSL using gou query engine
+	// 5. Execute QueryDSL using gou query engine
 	records, err := h.executeDSL(result.DSL)
 	if err != nil {
 		return &types.Result{
@@ -181,7 +184,7 @@ func (h *Handler) SearchWithContext(ctx *agentContext.Context, req *types.Reques
 		}, nil
 	}
 
-	// 5. Determine the primary model for result formatting
+	// 6. Determine the primary model for result formatting
 	// Use the "from" table from DSL, or first model
 	primaryModelID := modelIDs[0]
 	if result.DSL.From != nil && result.DSL.From.Name != "" {
@@ -199,7 +202,7 @@ func (h *Handler) SearchWithContext(ctx *agentContext.Context, req *types.Reques
 		primaryModel, _ = model.Get(primaryModelID) // May be nil, that's ok
 	}
 
-	// 6. Convert records to ResultItems
+	// 7. Convert records to ResultItems
 	items := h.convertToResultItems(records, primaryModelID, primaryModel, req.Source)
 
 	// Apply limit
@@ -207,7 +210,7 @@ func (h *Handler) SearchWithContext(ctx *agentContext.Context, req *types.Reques
 		items = items[:maxResults]
 	}
 
-	// 7. Convert DSL to map for storage
+	// 8. Convert DSL to map for storage
 	dslMap := h.dslToMap(result.DSL)
 
 	return &types.Result{
@@ -282,31 +285,52 @@ func (h *Handler) buildModelSchema(mod *model.Model) map[string]interface{} {
 	}
 }
 
-// executeDSL executes the QueryDSL and returns records
-func (h *Handler) executeDSL(dsl interface{}) ([]map[string]interface{}, error) {
-	// Get the default query engine
+// sanitizeDSL cleans up LLM-generated DSL to remove unsupported constructs.
+// The QueryDSL engine does not support wildcard "*" in select fields;
+// an empty select list naturally returns all columns.
+func (h *Handler) sanitizeDSL(dsl *gou.QueryDSL) {
+	if dsl == nil {
+		return
+	}
+
+	if len(dsl.Select) > 0 {
+		cleaned := make([]gou.Expression, 0, len(dsl.Select))
+		for _, expr := range dsl.Select {
+			if expr.Field != "*" {
+				cleaned = append(cleaned, expr)
+			}
+		}
+		dsl.Select = cleaned
+	}
+}
+
+// executeDSL executes the QueryDSL and returns records.
+// Uses recover to convert panics from MustGet into errors.
+func (h *Handler) executeDSL(dsl interface{}) (records []map[string]interface{}, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("query execution panic: %v", r)
+		}
+	}()
+
 	engine, err := query.Select("default")
 	if err != nil {
 		return nil, fmt.Errorf("query engine not found: %w", err)
 	}
 
-	// Marshal DSL to JSON
 	dslJSON, err := json.Marshal(dsl)
 	if err != nil {
 		return nil, fmt.Errorf("failed to marshal DSL: %w", err)
 	}
 
-	// Load and execute the query
 	q, err := engine.Load(json.RawMessage(dslJSON))
 	if err != nil {
 		return nil, fmt.Errorf("failed to load DSL: %w", err)
 	}
 
-	// Execute query
 	rawRecords := q.Get(nil)
 
-	// Convert to map[string]interface{}
-	records := make([]map[string]interface{}, 0, len(rawRecords))
+	records = make([]map[string]interface{}, 0, len(rawRecords))
 	for _, rec := range rawRecords {
 		records = append(records, map[string]interface{}(rec))
 	}