Fix FlagRerank max_length issue. (#5366)

### What problem does this PR solve?

#5352

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/db/services/dialog_service.py

@@ -859,7 +859,7 @@ Output:
 
 
 def reasoning(chunk_info: dict, question: str, chat_mdl: LLMBundle, embd_mdl: LLMBundle,
-              tenant_ids: list[str], kb_ids: list[str], prompt_config, MAX_SEARCH_LIMIT: int = 3,
+              tenant_ids: list[str], kb_ids: list[str], prompt_config, MAX_SEARCH_LIMIT: int = 6,
               top_n: int = 5, similarity_threshold: float = 0.4, vector_similarity_weight: float = 0.3):
     BEGIN_SEARCH_QUERY = "<|begin_search_query|>"
     END_SEARCH_QUERY = "<|end_search_query|>"

rag/llm/rerank_model.py

@@ -130,12 +130,12 @@ class DefaultRerank(Base):
 
         self._dynamic_batch_size = old_dynamic_batch_size
         return np.array(res)
-    
 
     def _compute_batch_scores(self, batch_pairs, max_length=None):
         if max_length is None:
-            max_length = self._model.max_length
-        scores = self._model.compute_score(batch_pairs, max_length=max_length)
+            scores = self._model.compute_score(batch_pairs)
+        else:
+            scores = self._model.compute_score(batch_pairs, max_length=max_length)
         scores = sigmoid(np.array(scores)).tolist()
         return scores