diff --git a/cpp/src/arrow/compute/kernels/scalar_cast_nested.cc b/cpp/src/arrow/compute/kernels/scalar_cast_nested.cc index 0033d89fc40fc..f8199f8708175 100644 --- a/cpp/src/arrow/compute/kernels/scalar_cast_nested.cc +++ b/cpp/src/arrow/compute/kernels/scalar_cast_nested.cc @@ -363,10 +363,6 @@ struct CastStruct { const auto& in_field = in_type.field(in_field_index); // If there are more in_fields check if they match the out_field. if (in_field->name() == out_field->name()) { - if (in_field->nullable() && !out_field->nullable()) { - return Status::TypeError("cannot cast nullable field to non-nullable field: ", - in_type.ToString(), " ", out_type.ToString()); - } // Found matching in_field and out_field. fields_to_select[out_field_index++] = in_field_index; // Using the same in_field for multiple out_fields is not allowed. @@ -412,8 +408,14 @@ struct CastStruct { } else { const auto& values = (in_array.child_data[field_index].ToArrayData()->Slice( in_array.offset, in_array.length)); - ARROW_ASSIGN_OR_RAISE(Datum cast_values, - Cast(values, target_type, options, ctx->exec_context())); + const auto& target_field = out->type()->field(out_field_index++); + if (!target_field->nullable() && values->null_count > 0) { + return Status::TypeError("field '", target_field->name(), + "' has nulls. Can't cast to non-nullable type ", + target_field->type()->ToString()); + } + ARROW_ASSIGN_OR_RAISE(Datum cast_values, Cast(values, target_field->type(), + options, ctx->exec_context())); DCHECK(cast_values.is_array()); out_array->child_data.push_back(cast_values.array()); } diff --git a/cpp/src/arrow/compute/kernels/scalar_cast_test.cc b/cpp/src/arrow/compute/kernels/scalar_cast_test.cc index 33a01425508e0..c5551156a8ae3 100644 --- a/cpp/src/arrow/compute/kernels/scalar_cast_test.cc +++ b/cpp/src/arrow/compute/kernels/scalar_cast_test.cc @@ -2943,7 +2943,7 @@ TEST(Cast, StructToDifferentNullabilityStruct) { CheckCast(src_non_nullable, dest3_nullable); } { - // But NOT OK to go from nullable to non-nullable... + // But when going from nullable to non-nullable, all data must be non-null... std::vector> fields_src_nullable = { std::make_shared("a", int8(), true), std::make_shared("b", int8(), true), @@ -2965,27 +2965,30 @@ TEST(Cast, StructToDifferentNullabilityStruct) { const auto options1_non_nullable = CastOptions::Safe(dest1_non_nullable); EXPECT_RAISES_WITH_MESSAGE_THAT( TypeError, - ::testing::HasSubstr("cannot cast nullable field to non-nullable field"), + ::testing::HasSubstr( + "field 'a' has nulls. Can't cast to non-nullable type int64"), Cast(src_nullable, options1_non_nullable)); std::vector> fields_dest2_non_nullable = { std::make_shared("a", int64(), false), std::make_shared("c", int64(), false)}; const auto dest2_non_nullable = arrow::struct_(fields_dest2_non_nullable); - const auto options2_non_nullable = CastOptions::Safe(dest2_non_nullable); + const auto options2_non_nullable = CastOptions::Unsafe(dest2_non_nullable); EXPECT_RAISES_WITH_MESSAGE_THAT( TypeError, - ::testing::HasSubstr("cannot cast nullable field to non-nullable field"), + ::testing::HasSubstr( + "field 'a' has nulls. Can't cast to non-nullable type int64"), Cast(src_nullable, options2_non_nullable)); - std::vector> fields_dest3_non_nullable = { + std::shared_ptr c_dest_no_nulls; + c_dest_no_nulls = ArrayFromJSON(int64(), "[9, 11, 44]"); + std::vector> fields_dest_no_nulls = { std::make_shared("c", int64(), false)}; - const auto dest3_non_nullable = arrow::struct_(fields_dest3_non_nullable); - const auto options3_non_nullable = CastOptions::Safe(dest3_non_nullable); - EXPECT_RAISES_WITH_MESSAGE_THAT( - TypeError, - ::testing::HasSubstr("cannot cast nullable field to non-nullable field"), - Cast(src_nullable, options3_non_nullable)); + ASSERT_OK_AND_ASSIGN(auto dest_no_nulls, + StructArray::Make({c_dest_no_nulls}, fields_dest_no_nulls)); + const auto options3_non_nullable = + CastOptions::Unsafe(arrow::struct_(fields_dest_no_nulls)); + CheckCast(src_nullable, dest_no_nulls, options3_non_nullable); } }