Optimized Truncate Function (#2453)

### What problem does this PR solve?

_Optimized Truncate Function_

Issue link: (#2033)

### Type of change

- [x] Test cases
- [x] Other (please describe): Optimized

Author: kche0169

python/infinity_http.py

@@ -921,12 +921,8 @@ def to_result(self):
                 if k not in df_dict:
                     df_dict[k] = ()
                 tup = df_dict[k]
-                if isinstance(res[k], str) and len(res[k]) > 0 and res[k][0] == " ":
+                if isinstance(res[k], (int, float)):
                     new_tup = tup + (res[k],)
-                elif isinstance(res[k], (int, float)):
-                    new_tup = tup + (res[k],)
-                elif res[k].isdigit() or is_float(res[k]):
-                    new_tup = tup + (eval(res[k]),)
                 elif is_list(res[k]):
                     new_tup = tup + (ast.literal_eval(res[k]),)
                 elif is_date(res[k]):

python/test_pysdk/test_select.py

@@ -1038,11 +1038,12 @@ def test_select_truncate(self, suffix):
 
         res, extra_res = table_obj.output(["trunc(c1, 14)",  "trunc(c2, 2)", "trunc(c3, 2)"]).to_df()
         print(res)
-        pd.testing.assert_frame_equal(res, pd.DataFrame({'(c1 trunc 14)': (" 2.12300000000000", " -2.12300000000000", " 2.00000000000000", " 2.10000000000000"),
-                                                         '(c2 trunc 2)': (" 2.12", " -2.12", " 2.00", " 2.10"),
-                                                         '(c3 trunc 2)': (" 2.12", " -2.12", " 2.00", " 2.10")
+        print(res.dtypes)
+        pd.testing.assert_frame_equal(res, pd.DataFrame({'(c1 trunc 14)': ("2.12300000000000", "-2.12300000000000", "2.00000000000000", "2.10000000000000"),
+                                                         '(c2 trunc 2)': ("2.12", "-2.12", "2.00", "2.10"),
+                                                         '(c3 trunc 2)': ("2.12", "-2.12", "2.00", "2.10")
                                                          })
-                                      .astype({'(c1 trunc 14)': dtype('str_'), '(c2 trunc 2)': dtype('str_'), '(c3 trunc 2)': dtype('str_')}))
+                                      .astype({'(c1 trunc 14)': dtype('object'), '(c2 trunc 2)': dtype('object'), '(c3 trunc 2)': dtype('object')}))
 
 
         res = db_obj.drop_table("test_select_truncate" + suffix)
@@ -1061,6 +1062,7 @@ def test_select_reverse(self, suffix):
 
         res, extra_res = table_obj.output(["reverse(c1)", "reverse(c2)"]).to_df()
         print(res)
+        print(res.dtypes)
         pd.testing.assert_frame_equal(res, pd.DataFrame({'reverse(c1)': ('cba', '321a', 'c', 'nmlkjihgfedcba'),
                                                          'reverse(c2)': ('CBA', '321a', 'C', 'NMLKJIHGFEDCBA')})
                                       .astype({'reverse(c1)': dtype('str_'), 'reverse(c2)': dtype('str_')}))

src/function/scalar/truncate.cpp

@@ -50,17 +50,16 @@ inline void TruncFunction::Run(DoubleT left, BigIntT right, VarcharT &result, Co
     }
 
     char buffer[MinBufferSize];  
-    buffer[0] =' ';
-    
+
     right = (right > MaxRight) ? MaxRight : right;  
 
-    int len = std::snprintf(buffer + 1, sizeof(buffer) - 2, "%.*f", (int)right, left);
+    int len = std::snprintf(buffer, sizeof(buffer) - 1, "%.*f", (int)right, left);
     if (len < 0) {
         Status status = Status::InvalidDataType();
         RecoverableError(status);
         return;
     }
-    std::string truncated_str(buffer, len + 1);
+    std::string truncated_str(buffer, len);
     result_ptr->AppendVarcharInner(truncated_str, result);
 
 }
@@ -76,15 +75,15 @@ inline void TruncFunction::Run(FloatT left, BigIntT right, VarcharT &result, Col
         return;
     } 
     char buffer[MinBufferSize]; 
-    buffer[0] =' '; 
+
     right = (right >  MaxRight) ?  MaxRight : right;
-    int len = std::snprintf(buffer + 1, sizeof(buffer) - 2, "%.*f", (int)right, left);
+    int len = std::snprintf(buffer, sizeof(buffer) - 1, "%.*f", (int)right, left);
     if (len < 0) {
         Status status = Status::InvalidDataType();
         RecoverableError(status);
         return;
     }
-    std::string truncated_str(buffer, len + 1);
+    std::string truncated_str(buffer, len);
     result_ptr->AppendVarcharInner(truncated_str, result);
 }