enhance: simplify the structure of search_params

Signed-off-by: lixinguo <xinguo.li@zilliz.com>

pymilvus/client/prepare.py

@@ -939,7 +939,6 @@ def search_requests_with_expr(
 
         search_params = {
             "topk": limit,
-            "params": params,
             "round_decimal": round_decimal,
             "ignore_growing": ignore_growing,
         }
@@ -979,6 +978,18 @@ def search_requests_with_expr(
         if param.get(HINTS) is not None:
             search_params[HINTS] = param[HINTS]
 
+        # after 2.5.1, all parameters of search_params can be written into one layer
+        # no more parameters will be written searchParams.params
+        # to ensure compatibility and milvus can still get a json format parameter
+        # try to write all the parameters under searchParams into searchParams.Params
+        for key, value in search_params.items():
+            if key in params and params[key] != value:
+                raise ParamError(
+                    message=f"ambiguous parameter: {key}, in search_param: {value}, in search_param: {params[key]}"
+                )
+            params[key] = value
+        search_params["params"] = params
+
         req_params = [
             common_types.KeyValuePair(key=str(key), value=utils.dumps(value))
             for key, value in search_params.items()