suxiaogang223 opened a new pull request, #2086:
URL: https://github.com/apache/orc/pull/2086
close: #2079
relate pr: #2055
Introduce fallback logic in the C++ reader to set hasNull to true when the
field is missing, similar to the Java implementation. The Java implementation
includes the following logic:
```java
if (stats.hasHasNull()) {
hasNull = stats.getHasNull();
} else {
hasNull = true;
}
```
In contrast, the C++ implementation directly uses the has_null value without
any fallback logic:
```c++
ColumnStatisticsImpl::ColumnStatisticsImpl(const proto::ColumnStatistics&
pb) {
stats_.setNumberOfValues(pb.number_of_values());
stats_.setHasNull(pb.has_null());
}
```
We encountered an issue with the C++ implementation of the ORC reader when
handling ORC files written with version 0.12. Specifically, files written in
this version do not include the hasNull field in the column statistics
metadata. While the Java implementation of the ORC reader handles this
gracefully by defaulting hasNull to true when the field is absent, the C++
implementation does not handle this scenario correctly. **This issue prevents
predicates like IS NULL from being pushed down to the ORC reader!!! As a
result, all rows in the file are filtered out, leading to incorrect query
results :(** I have tested this using [Doris](https://github.com/apache/doris)
external pipeline: https://github.com/apache/doris/pull/45104
https://github.com/apache/doris-thirdparty/pull/259 No
Closes #2082 from suxiaogang223/fix_has_null.
Authored-by: Socrates <[email protected]>
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