pitrou commented on code in PR #41975:
URL: https://github.com/apache/arrow/pull/41975#discussion_r1653237808
##########
cpp/src/arrow/compute/exec.cc:
##########
@@ -498,15 +510,37 @@ struct NullGeneralization {
return PERHAPS_NULL;
}
+ static type Get(const ChunkedArray& chunk_array) {
+ if (chunk_array.num_chunks() == 0) {
+ return ALL_VALID;
+ }
+ if (chunk_array.null_count() == chunk_array.length()) {
Review Comment:
This does not follow the same constraint as Array above: _"Do not count the
bits if they haven't been counted already"_.
I think you should instead just iterate on the chunks, such as (untested):
```c++
static type Get(const ArraySpan& array) {
// Do not count the bits if they haven't been counted already
if ((arr.null_count == 0) || (arr.buffers[0].data == nullptr)) {
return ALL_VALID;
}
if (arr.null_count == arr.length) {
return ALL_NULL;
}
return PERHAPS_NULL;
}
static type Get(const ChunkedArray& chunk_array) {
std::optional<type> current_gen;
for (const auto& chunk : chunk_array.chunks()) {
if (chunk->length() == 0) {
continue;
}
chunk_gen = Get(*chunk);
if (current_gen.has_value() && chunk_gen != *current_gen) {
return PERHAPS_NULL;
}
current_gen = chunk_gen;
}
return current_gen.value_or(ALL_VALID);
}
```
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