[FLINK-38319][python] Allow TO_TIMESTAMP_LTZ to accept expressions other than literal in PyFlink (#26987)

Author: charlesdong1991

flink-python/pyflink/table/expressions.py

@@ -355,15 +355,15 @@ def to_timestamp_ltz(*args) -> Expression:
                                         "UTC"))  # string with format and timezone
     """
     if len(args) == 1:
-        return _unary_op("toTimestampLtz", lit(args[0]))
+        return _unary_op("toTimestampLtz", args[0])
 
     # For two arguments case (numeric + precision or string + format)
     elif len(args) == 2:
-        return _binary_op("toTimestampLtz", lit(args[0]), lit(args[1]))
+        return _binary_op("toTimestampLtz", args[0], args[1])
 
     # For three arguments case (string + format + timezone)
     else:
-        return _ternary_op("toTimestampLtz", lit(args[0]), lit(args[1]), lit(args[2]))
+        return _ternary_op("toTimestampLtz", args[0], args[1], args[2])
 
 
 @PublicEvolving()

flink-python/pyflink/table/tests/test_expression.py

@@ -295,6 +295,12 @@ def test_expressions(self):
         self.assertEqual("TO_TIMESTAMP_LTZ('2023-01-01 00:00:00', 'yyyy-MM-dd HH:mm:ss', 'UTC')",
                          str(to_timestamp_ltz("2023-01-01 00:00:00", "yyyy-MM-dd HH:mm:ss", "UTC")))
         self.assertEqual("TO_TIMESTAMP_LTZ(123, 0)", str(to_timestamp_ltz(123, 0)))
+        self.assertEqual("TO_TIMESTAMP_LTZ(a)", str(to_timestamp_ltz(expr1)))
+        self.assertEqual("TO_TIMESTAMP_LTZ(a, 0)", str(to_timestamp_ltz(expr1, 0)))
+        self.assertEqual("TO_TIMESTAMP_LTZ(a, 'MM/dd/yyyy HH:mm:ss')",
+                         str(to_timestamp_ltz(expr1, "MM/dd/yyyy HH:mm:ss")))
+        self.assertEqual("TO_TIMESTAMP_LTZ(a, 'MM/dd/yyyy HH:mm:ss', 'UTC')",
+                         str(to_timestamp_ltz(expr1, "MM/dd/yyyy HH:mm:ss", "UTC")))
         self.assertEqual("toTimestamp('1970-01-01 08:01:40')",
                          str(to_timestamp('1970-01-01 08:01:40')))
         self.assertEqual("toTimestamp('1970-01-01 08:01:40', 'yyyy-MM-dd HH:mm:ss')",