Fix cast negative number string as unsigned int (#1762) (#1768)

dbms/src/Functions/FunctionsTiDBConversion.h

@@ -405,19 +405,25 @@ struct TiDBConvertToInteger
                 context.getDAGContext()->handleTruncateError("cast str as int");
             return static_cast<T>(0);
         }
-        if constexpr (to_unsigned)
+        bool is_negative = false;
+        if (int_string.data[0] == '-')
+        {
+            is_negative = true;
+        }
+        if (!is_negative)
         {
             auto [value, err] = toUInt<T>(int_string);
             if (err == OVERFLOW_ERR)
                 context.getDAGContext()->handleOverflowError("cast str as int");
-            return value;
+            return static_cast<T>(value);
         }
         else
         {
+            /// TODO: append warning CastAsSignedOverflow if try to cast negative value to unsigned
             auto [value, err] = toInt<T>(int_string);
             if (err == OVERFLOW_ERR)
                 context.getDAGContext()->handleOverflowError("cast str as int");
-            return value;
+            return static_cast<T>(value);
         }
     }
 

tests/fullstack-test/expr/cast_string_as_int.test

@@ -6,17 +6,21 @@ mysql> insert into test.t values('2006-01')
 
 func> wait_table test t
 
-mysql> set @@tidb_isolation_read_engines='tiflash'
-
 # Issue https://github.com/pingcap/tics/issues/1469
 
-mysql> select * from test.t where cast(a as signed) = -123
+mysql> set @@tidb_isolation_read_engines='tiflash'; select * from test.t where cast(a as signed) = -123
++------+
+| a    |
++------+
+| -123 |
++------+
+mysql> set @@tidb_isolation_read_engines='tiflash'; select * from test.t where cast(a as unsigned) = cast(-123 as unsigned)
 +------+
 | a    |
 +------+
 | -123 |
 +------+
-mysql> select * from test.t where cast(a as signed) = 2006
+mysql> set @@tidb_isolation_read_engines='tiflash'; select * from test.t where cast(a as signed) = 2006
 +---------+
 | a       |
 +---------+