wjones127 commented on code in PR #14749:
URL: https://github.com/apache/arrow/pull/14749#discussion_r1034147079
##########
cpp/src/arrow/compute/kernels/scalar_nested_test.cc:
##########
@@ -168,6 +173,20 @@ TEST(TestScalarNested, ListSliceFixedOutput) {
expected = ArrayFromJSON(fixed_size_list(value_type, 2),
"[[3, null], [null, null], [null, null],
null]");
CheckScalarUnary("list_slice", input, expected, &args);
+
+ args.start = 1;
+ args.stop = std::nullopt;
+ expected = ArrayFromJSON(fixed_size_list(value_type, 2),
+ "[[2, 3], [5, null], [null, null], null]");
+ if (input->type()->id() == Type::FIXED_SIZE_LIST) {
+ CheckScalarUnary("list_slice", input, expected, &args);
+ } else {
+ EXPECT_RAISES_WITH_MESSAGE_THAT(
+ NotImplemented,
+ ::testing::HasSubstr("Unable to produce FixedSizeListArray from "
+ "non-FixedSizeListArray without `stop` being
set."),
+ CallFunction("list_slice", {input}, &args));
+ }
Review Comment:
Is this a case that is possible?
```suggestion
}
args.start = 3;
args.stop = std::nullopt;
expected = ArrayFromJSON(fixed_size_list(value_type, 0),
"[[], [], [], null]");
if (input->type()->id() == Type::FIXED_SIZE_LIST) {
CheckScalarUnary("list_slice", input, expected, &args);
}
```
##########
cpp/src/arrow/compute/kernels/scalar_nested.cc:
##########
@@ -131,13 +124,26 @@ struct ListSlice {
list_type->id() == arrow::Type::FIXED_SIZE_LIST);
std::unique_ptr<ArrayBuilder> builder;
+ // should have been checked in resolver
+ // if stop not set, then cannot return fixed size list without input being
fixed size
+ // list b/c we cannot determine the max list element in type resolving.
+ DCHECK(opts.stop.has_value() ||
+ (!opts.stop.has_value() && (!return_fixed_size_list ||
+ list_type->id() ==
arrow::Type::FIXED_SIZE_LIST)));
+
// construct array values
if (return_fixed_size_list) {
- RETURN_NOT_OK(MakeBuilder(
- ctx->memory_pool(),
- fixed_size_list(value_type,
- static_cast<int32_t>(opts.stop.value() -
opts.start)),
- &builder));
+ const auto stop = [&]() {
+ if (opts.stop.has_value()) {
+ return static_cast<int32_t>(opts.stop.value());
+ } else {
+ DCHECK_EQ(list_type->id(), arrow::Type::FIXED_SIZE_LIST);
+ return checked_cast<const
FixedSizeListType*>(list_type)->list_size();
+ }
+ }();
+ const auto size = std::max(stop - static_cast<int32_t>(opts.start), 0);
Review Comment:
Isn't this guaranteed to be non-negative?
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