fix opendal config 'oss_table' and 'max_allowed_packet' (#8611)

### What problem does this PR solve?

Fix the config option name of the opendal table name and setting of
'max_allowed_packet'.

### Type of change

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

Signed-off-by: He Wang <wanghechn@qq.com>

conf/service_conf.yaml

 # opendal:
 #   scheme: 'mysql'  # Storage type, such as s3, oss, azure, etc.
 #   config:
-#     oss_table: 'your_table_name'
+#     oss_table: 'opendal_storage'
 # user_default_llm:
 #   factory: 'Tongyi-Qianwen'
 #   api_key: 'sk-xxxxxxxxxxxxx'

rag/utils/opendal_conn.py

 import opendal
 import logging
 import pymysql
-import yaml
 
+from api.utils import get_base_config
 from rag.utils import singleton
 
-SERVICE_CONF_PATH = "conf/service_conf.yaml"
 
 CREATE_TABLE_SQL = """
 CREATE TABLE IF NOT EXISTS `{}` (
 """
 
 
-def get_opendal_config_from_yaml(yaml_path=SERVICE_CONF_PATH):
+def get_opendal_config():
     try:
-        with open(yaml_path, 'r') as f:
-            config = yaml.safe_load(f)
-
-        opendal_config = config.get('opendal', {})
-        kwargs = {}
+        opendal_config = get_base_config('opendal', {})
         if opendal_config.get("scheme") == 'mysql':
-            mysql_config = config.get('mysql', {})
+            mysql_config = get_base_config('mysql', {})
+            max_packet = mysql_config.get("max_allowed_packet", 134217728)
             kwargs = {
                 "scheme": "mysql",
                 "host": mysql_config.get("host", "127.0.0.1"),
                 "user": mysql_config.get("user", "root"),
                 "password": mysql_config.get("password", ""),
                 "database": mysql_config.get("name", "test_open_dal"),
-                "table": opendal_config.get("config").get("table", "opendal_storage")
+                "table": opendal_config.get("config").get("oss_table", "opendal_storage"),
+                "max_allowed_packet": str(max_packet)
             }
-            kwargs["connection_string"] = f"mysql://{kwargs['user']}:{kwargs['password']}@{kwargs['host']}:{kwargs['port']}/{kwargs['database']}"
+            kwargs["connection_string"] = f"mysql://{kwargs['user']}:{kwargs['password']}@{kwargs['host']}:{kwargs['port']}/{kwargs['database']}?max_allowed_packet={max_packet}"
         else:
             scheme = opendal_config.get("scheme")
             config_data = opendal_config.get("config", {})
 @singleton
 class OpenDALStorage:
     def __init__(self):
-        self._kwargs = get_opendal_config_from_yaml()
+        self._kwargs = get_opendal_config()
         self._scheme = self._kwargs.get('scheme', 'mysql')
         if self._scheme == 'mysql':
             self.init_db_config()
             )
             cursor = conn.cursor()
             max_packet = self._kwargs.get('max_allowed_packet', 4194304)  # Default to 4MB if not specified
-            cursor.execute(SET_MAX_ALLOWED_PACKET_SQL, (max_packet,))
+            cursor.execute(SET_MAX_ALLOWED_PACKET_SQL.format(max_packet))
             conn.commit()
             cursor.close()
             conn.close()