feat:增加TextToSql文档

docs/Web/AI/Langchain.md

@@ -171,4 +171,72 @@ agent.stream({"messages": [message]},
 ):
 ```
 
-  调用模型的时候需要传递`thread_id`。    
+  调用模型的时候需要传递`thread_id`。    
+::: tip
+通常还需要构建一个`用户-问题标题`的数据库，方便查询用户的所有历史回答。     
+问题标题可以再调一次模型总结。   
+:::
+
+# 七、实战
+## 7.1 后端
+```python
+async def query_agent(request: ChatRequest):
+    try:
+        message = HumanMessage(content=request.message)
+
+        # 流式调用Agent
+        for chunk, metadata in agent.stream(
+                {"messages": [message]},
+                {"configurable": {"thread_id": request.thread_id}},
+                stream_mode="messages"
+        ):
+            if isinstance(chunk, AIMessageChunk) and chunk.content:
+                yield chunk.content
+
+        # 总结对话标题并保存
+        if not exists_session(request.thread_id, request.username):
+            title = generate_title(get_messages(request.thread_id))
+            save_session(request.thread_id, request.username, title)
+
+    except Exception as e:
+        print(f"\n[错误]: {str(e)}")
+        yield "信息检索失败，请重新输入问题提问"
+
+
+@router.post("/chat/stream")
+async def chat_endpoint(request: ChatRequest):
+    """流式对话"""
+    return StreamingResponse(
+        query_agent(request),
+        media_type="text/event-stream"
+    )       
+```
+
+## 7.2 前端
+```typescript
+const sendMessage = async () => {
+  try {
+    const response = await fetch(
+        "/chief-agent-api/chat/stream",
+        {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify(message)
+        }
+    );
+
+    const reader = response.body!.getReader();
+    const decoder = new TextDecoder("utf-8");
+    let aiText = "";
+
+    while (true) {
+      const { value, done } = await reader.read();
+      if (done) break;
+
+      aiText += decoder.decode(value, { stream: true });
+    }
+  } finally {
+    loading = false;
+  }
+};
+```