diff --git a/mishards/exception_codes.py b/mishards/exception_codes.py
index 37492f25d4..ecb2469562 100644
--- a/mishards/exception_codes.py
+++ b/mishards/exception_codes.py
@@ -2,6 +2,8 @@ INVALID_CODE = -1
 
 CONNECT_ERROR_CODE = 10001
 CONNECTTION_NOT_FOUND_CODE = 10002
+DB_ERROR_CODE = 10003
 
 TABLE_NOT_FOUND_CODE = 20001
-INVALID_ARGUMENT = 20002
+INVALID_ARGUMENT_CODE = 20002
+INVALID_DATE_RANGE_CODE = 20003
diff --git a/mishards/exception_handlers.py b/mishards/exception_handlers.py
index 6207f2088c..2518b64b3e 100644
--- a/mishards/exception_handlers.py
+++ b/mishards/exception_handlers.py
@@ -29,6 +29,9 @@ def resp_handler(err, error_code):
     if resp_class == milvus_pb2.TableRowCount:
         return resp_class(status=status, table_row_count=-1)
 
+    if resp_class == milvus_pb2.TableName:
+        return resp_class(status=status, table_name=[])
+
     status.error_code = status_pb2.UNEXPECTED_ERROR
     return status
 
@@ -41,3 +44,13 @@ def TableNotFoundErrorHandler(err):
 def InvalidArgumentErrorHandler(err):
     logger.error(err)
     return resp_handler(err, status_pb2.ILLEGAL_ARGUMENT)
+
+@server.errorhandler(exceptions.DBError)
+def DBErrorHandler(err):
+    logger.error(err)
+    return resp_handler(err, status_pb2.UNEXPECTED_ERROR)
+
+@server.errorhandler(exceptions.InvalidRangeError)
+def InvalidArgumentErrorHandler(err):
+    logger.error(err)
+    return resp_handler(err, status_pb2.ILLEGAL_RANGE)
diff --git a/mishards/exceptions.py b/mishards/exceptions.py
index 4686cf674f..2aa2b39eb9 100644
--- a/mishards/exceptions.py
+++ b/mishards/exceptions.py
@@ -13,8 +13,14 @@ class ConnectionConnectError(BaseException):
 class ConnectionNotFoundError(BaseException):
     code = codes.CONNECTTION_NOT_FOUND_CODE
 
+class DBError(BaseException):
+    code = codes.DB_ERROR_CODE
+
 class TableNotFoundError(BaseException):
     code = codes.TABLE_NOT_FOUND_CODE
 
 class InvalidArgumentError(BaseException):
-    code = codes.INVALID_ARGUMENT
+    code = codes.INVALID_ARGUMENT_CODE
+
+class InvalidRangeError(BaseException):
+    code = codes.INVALID_DATE_RANGE_CODE
diff --git a/mishards/service_handler.py b/mishards/service_handler.py
index 128667d9b6..536a17c4e3 100644
--- a/mishards/service_handler.py
+++ b/mishards/service_handler.py
@@ -5,10 +5,12 @@ from contextlib import contextmanager
 from collections import defaultdict
 
 from sqlalchemy import and_
+from sqlalchemy import exc as sqlalchemy_exc
 
 from concurrent.futures import ThreadPoolExecutor
 from milvus.grpc_gen import milvus_pb2, milvus_pb2_grpc, status_pb2
 from milvus.grpc_gen.milvus_pb2 import TopKQueryResult
+from milvus.client.Abstract import Range
 from milvus.client import types
 
 from mishards import (db, settings, exceptions)
@@ -44,7 +46,7 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
         return ((start.year-1900)*10000 + (start.month-1)*100 + start.day
                 , (end.year-1900)*10000 + (end.month-1)*100 + end.day)
 
-    def _range_to_date(self, range_obj):
+    def _range_to_date(self, range_obj, metadata=None):
         try:
             start = datetime.datetime.strptime(range_obj.start_date, '%Y-%m-%d')
             end = datetime.datetime.strptime(range_obj.end_date, '%Y-%m-%d')
@@ -52,15 +54,19 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
         except (ValueError, AssertionError):
             raise exceptions.InvalidRangeError('Invalid time range: {} {}'.format(
                     range_obj.start_date, range_obj.end_date
-                ))
+                ), metadata=metadata)
 
         return self._format_date(start, end)
 
     def _get_routing_file_ids(self, table_id, range_array, metadata=None):
-        table = db.Session.query(Tables).filter(and_(
-                Tables.table_id==table_id,
-                Tables.state!=Tables.TO_DELETE
-            )).first()
+        # PXU TODO: Implement Thread-local Context
+        try:
+            table = db.Session.query(Tables).filter(and_(
+                    Tables.table_id==table_id,
+                    Tables.state!=Tables.TO_DELETE
+                )).first()
+        except sqlalchemy_exc.SQLAlchemyError as e:
+            raise exceptions.DBError(message=str(e), metadata=metadata)
 
         if not table:
             raise exceptions.TableNotFoundError(table_id, metadata=metadata)
@@ -111,8 +117,8 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
         return topk_query_result
 
     def _do_query(self, table_id, table_meta, vectors, topk, nprobe, range_array=None, **kwargs):
-        range_array = [self._range_to_date(r) for r in range_array] if range_array else None
         metadata = kwargs.get('metadata', None)
+        range_array = [self._range_to_date(r, metadata=metadata) for r in range_array] if range_array else None
         routing = self._get_routing_file_ids(table_id, range_array, metadata=metadata)
         logger.info('Routing: {}'.format(routing))
 
@@ -362,7 +368,10 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
     @mark_grpc_method
     def ShowTables(self, request, context):
         logger.info('ShowTables')
-        _status, _results = self.connection.show_tables()
+        metadata = {
+            'resp_class': milvus_pb2.TableName
+        }
+        _status, _results = self.connection(metadata=metadata).show_tables()
 
         if not _status.OK():
             _results = []