diff --git a/tests/system-test/0-others/udfpy/sf_concat_nch.py b/tests/system-test/0-others/udfpy/sf_concat_nch.py
index c64bfa8ad3a1e8482e09a7264cc4bff07701ecbc..84d8eb2c961c11282784f81b6206a36fba0f2edc 100644
--- a/tests/system-test/0-others/udfpy/sf_concat_nch.py
+++ b/tests/system-test/0-others/udfpy/sf_concat_nch.py
@@ -14,10 +14,14 @@ def process(block):
         for j in range(ncols):
             val = block.data(i, j)
             if val is None:
-                return [None]
+                row = None
+                break
             row.append(val.decode('utf_32_le'))
-        row_str = ''.join(row)
-        results.append(row_str.encode('utf_32_le'))
+        if row is None:
+            results.append(None)
+        else:        
+            row_str = ''.join(row)
+            results.append(row_str.encode('utf_32_le'))
     return results
 
 
diff --git a/tests/system-test/0-others/udfpy/sf_concat_var.py b/tests/system-test/0-others/udfpy/sf_concat_var.py
index 0a63821aa72d431b49aea452b84347de27ecc054..fc8292c718d5c8def7cebc87ee7938b2c7bd3849 100644
--- a/tests/system-test/0-others/udfpy/sf_concat_var.py
+++ b/tests/system-test/0-others/udfpy/sf_concat_var.py
@@ -14,9 +14,13 @@ def process(block):
         for j in range(ncols):
             val = block.data(i, j)
             if val is None:
-                return [None]
+                row = None
+                break
             row.append(val.decode('utf-8'))
-        results.append(''.join(row))
+        if row is None:
+            results.append(None)
+        else:    
+            results.append(''.join(row))
     return results
 
 
diff --git a/tests/system-test/0-others/udfpy_main.py b/tests/system-test/0-others/udfpy_main.py
index b4fd77f93a42e3dd74b314ecb55ef2407ddc0c4e..a2176a041ccaba16b0a59d4e094c992f6523cd94 100644
--- a/tests/system-test/0-others/udfpy_main.py
+++ b/tests/system-test/0-others/udfpy_main.py
@@ -73,7 +73,7 @@ class TDTestCase:
             'col9': 'float',
             'col10': 'double',
             'col11': 'bool',
-            'col12': 'varchar(20)',
+            'col12': 'varchar(120)',
             'col13': 'nchar(100)',
         }
         self.tag_dict = {
@@ -88,7 +88,7 @@ class TDTestCase:
             't9': 'float',
             't10': 'double',
             't11': 'bool',
-            't12': 'varchar(20)',
+            't12': 'varchar(120)',
             't13': 'nchar(100)',         
         }
 
@@ -149,7 +149,7 @@ class TDTestCase:
             'sf9': 'float',
             'sf10': 'double',
             'sf11': 'bool',
-            'sf12': 'varchar(20)',
+            'sf12': 'varchar(120)',
             'sf13': 'nchar(100)'
         }
         # agg function
@@ -165,7 +165,7 @@ class TDTestCase:
             'af9': 'float',
             'af10': 'double',
             'af11': 'bool',
-            'af12': 'varchar(20)',
+            'af12': 'varchar(120)',
             'af13': 'nchar(100)',
             'af14': 'timestamp'            
         }
@@ -399,7 +399,7 @@ class TDTestCase:
         stable = "meters"
         tbname = "d"
         count = 3
-        rows =  1000000
+        rows =  1000
         # do 
         self.create_table(stable, tbname, count)
         self.insert_data(tbname, rows)