Chenxi Li created ARROW-12804:
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Summary: [C++] Array methods IsNull and IsValid is confused for
NullType
Key: ARROW-12804
URL: https://issues.apache.org/jira/browse/ARROW-12804
Project: Apache Arrow
Issue Type: Bug
Components: C++
Reporter: Chenxi Li
I'm not sure if this is a bug or by design.
Array's method {{IsNull() {{and}} }}{{IsValid()}}{{}} is implemented as follows:
{code:c++}
/// \brief Return true if value at index is null. Does not boundscheck
bool IsNull(int64_t i) const {
return null_bitmap_data_ != NULLPTR &&
!BitUtil::GetBit(null_bitmap_data_, i + data_->offset);
}
/// \brief Return true if value at index is valid (not null). Does not
/// boundscheck
bool IsValid(int64_t i) const {
return null_bitmap_data_ == NULLPTR ||
BitUtil::GetBit(null_bitmap_data_, i + data_->offset);
}
{code}
According to the doc, "Arrays having a 0 null count may choose to not allocate
the null bitmap". But a null type array doesn't have a null bitmap. So for a
null type array, {{IsNull() }}always returns false, {{IsValid() }}always{{
}}returns true.
If this is by design, maybe a additional comments and docs should be added.
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