Add recursive type checking and fallback tests for casting array with…

… unsupported element types to string (#4449)

Signed-off-by: remzi <13716567376yh@gmail.com>

docs/supported_ops.md

@@ -16771,12 +16771,12 @@ and the accelerator produces the same result.
 <td> </td>
 <td> </td>
 <td> </td>
-<td>S</td>
+<td><em>PS<br/>the array's child type must also support being cast to string</em></td>
 <td> </td>
 <td> </td>
 <td> </td>
 <td> </td>
-<td><em>PS<br/>The array's child type must also support being cast to the desired child type;<br/>UTC is only supported TZ for child TIMESTAMP;<br/>unsupported child types CALENDAR, UDT</em></td>
+<td><em>PS<br/>The array's child type must also support being cast to the desired child type(s);<br/>UTC is only supported TZ for child TIMESTAMP;<br/>unsupported child types CALENDAR, UDT</em></td>
 <td> </td>
 <td> </td>
 <td> </td>
@@ -17175,12 +17175,12 @@ and the accelerator produces the same result.
 <td> </td>
 <td> </td>
 <td> </td>
-<td>S</td>
+<td><em>PS<br/>the array's child type must also support being cast to string</em></td>
 <td> </td>
 <td> </td>
 <td> </td>
 <td> </td>
-<td><em>PS<br/>The array's child type must also support being cast to the desired child type;<br/>UTC is only supported TZ for child TIMESTAMP;<br/>unsupported child types CALENDAR, UDT</em></td>
+<td><em>PS<br/>The array's child type must also support being cast to the desired child type(s);<br/>UTC is only supported TZ for child TIMESTAMP;<br/>unsupported child types CALENDAR, UDT</em></td>
 <td> </td>
 <td> </td>
 <td> </td>

integration_tests/src/main/python/cast_test.py

@@ -174,7 +174,7 @@ def test_cast_long_to_decimal_overflow():
 # casting these types to string is not exact match, marked as xfail when testing
 not_matched_gens_for_cast_to_string = [float_gen, double_gen, decimal_gen_neg_scale]
 # casting these types to string is not supported, marked as xfail when testing
-not_support_gens_for_cast_to_string = decimal_128_gens
+not_support_gens_for_cast_to_string = decimal_128_gens + [MapGen(ByteGen(False), ByteGen())]
 
 single_level_array_gens_for_cast_to_string = [ArrayGen(sub_gen) for sub_gen in basic_gens_for_cast_to_string]
 nested_array_gens_for_cast_to_string = [
@@ -188,13 +188,23 @@ def test_cast_long_to_decimal_overflow():
 
 def _assert_cast_to_string_equal (data_gen, conf):
     """
-    helper function for casting to string
+    helper function for casting to string of supported type
     """
     assert_gpu_and_cpu_are_equal_collect(
         lambda spark: unary_op_df(spark, data_gen).select(f.col('a').cast("STRING")),
         conf
     )
 
+def _assert_cast_to_string_fallback (data_gen, conf):
+    """
+    helper function for casting to string of unsupported type
+    """
+    assert_gpu_fallback_collect(
+        lambda spark: unary_op_df(spark, data_gen).select(f.col('a').cast("STRING")),
+        "Cast",
+        conf
+    )
+
 @pytest.mark.parametrize('data_gen', all_gens_for_cast_to_string, ids=idfn)
 @pytest.mark.parametrize('legacy', ['true', 'false'])
 def test_cast_array_to_string(data_gen, legacy):
@@ -219,12 +229,13 @@ def test_cast_array_with_unmatched_element_to_string(data_gen, legacy):
 
 @pytest.mark.parametrize('data_gen', [ArrayGen(sub) for sub in not_support_gens_for_cast_to_string], ids=idfn)
 @pytest.mark.parametrize('legacy', ['true', 'false'])
-@pytest.mark.xfail(reason='casting this type to string is not supported')
-def test_cast_array_with_unsupported_element_to_string(data_gen, legacy):
-    _assert_cast_to_string_equal(
+@allow_non_gpu('ProjectExec', 'Cast', 'Alias')
+def test_cast_array_with_unsupported_element_to_string_fallback(data_gen, legacy):
+    _assert_cast_to_string_fallback(
         data_gen, 
         {"spark.rapids.sql.castDecimalToString.enabled"     : 'true',
-         "spark.sql.legacy.castComplexTypesToString.enabled": legacy}
+         "spark.sql.legacy.castComplexTypesToString.enabled": legacy, 
+         "spark.sql.legacy.allowNegativeScaleOfDecimal": 'true'}
     )
 
 
@@ -285,11 +296,12 @@ def test_cast_struct_with_unmatched_element_to_string(data_gen, legacy):
 
 @pytest.mark.parametrize('data_gen', [StructGen([["first", element_gen]]) for element_gen in not_support_gens_for_cast_to_string], ids=idfn)
 @pytest.mark.parametrize('legacy', ['true', 'false'])
-@pytest.mark.xfail(reason='casting this type to string is not supported')
-def test_cast_struct_with_unsupported_element_to_string(data_gen, legacy):
-    _assert_cast_to_string_equal(
+@allow_non_gpu('ProjectExec', 'Cast', 'Alias')
+def test_cast_struct_with_unsupported_element_to_string_fallback(data_gen, legacy):
+    _assert_cast_to_string_fallback(
         data_gen, 
-        {"spark.rapids.sql.castDecimalToString.enabled"    : 'true',
-         "spark.sql.legacy.castComplexTypesToString.enabled": legacy}
+        {"spark.rapids.sql.castDecimalToString.enabled"     : 'true',
+         "spark.sql.legacy.castComplexTypesToString.enabled": legacy, 
+         "spark.sql.legacy.allowNegativeScaleOfDecimal": 'true'}
     )
 

sql-plugin/src/main/scala/com/nvidia/spark/rapids/GpuCast.scala

@@ -124,6 +124,9 @@ final class CastExprMeta[INPUT <: CastBase](
           case (fromChild, toChild) =>
             recursiveTagExprForGpuCheck(fromChild.dataType, toChild.dataType, depth + 1)
         }
+      case (ArrayType(elementType, _), StringType) =>
+        recursiveTagExprForGpuCheck(elementType, StringType, depth + 1)
+
       case (ArrayType(nestedFrom, _), ArrayType(nestedTo, _)) =>
         recursiveTagExprForGpuCheck(nestedFrom, nestedTo, depth + 1)
 

sql-plugin/src/main/scala/com/nvidia/spark/rapids/TypeChecks.scala

@@ -1270,10 +1270,11 @@ class CastChecks extends ExprChecks {
   val calendarChecks: TypeSig = none
   val sparkCalendarSig: TypeSig = CALENDAR + STRING
 
-  val arrayChecks: TypeSig = STRING + ARRAY.nested(commonCudfTypes + DECIMAL_128_FULL + NULL +
+  val arrayChecks: TypeSig = psNote(TypeEnum.STRING, "the array's child type must also support " +
+    "being cast to string") + ARRAY.nested(commonCudfTypes + DECIMAL_128_FULL + NULL +
       ARRAY + BINARY + STRUCT + MAP) +
-      psNote(TypeEnum.ARRAY, "The array's child type must also support being cast to " +
-          "the desired child type")
+      psNote(TypeEnum.ARRAY, "The array's child type must also support being cast to the " +
+          "desired child type(s)")
 
   val sparkArraySig: TypeSig = STRING + ARRAY.nested(all)