lokeshj1703 opened a new issue, #19636:
URL: https://github.com/apache/hudi/issues/19636
## Problem
When a table's ordering (precombine) field is a nullable column, a record
whose ordering value is null triggers a `NullPointerException` in the file
group reader's merge path.
`OrderingValues.create` maps the field value through the key-generation /
field-mapping function and, for the single-field case, returns whatever the
function produced. When the underlying column value is null the function
returns null, so `create` returns null and the resulting `BufferedRecord`
carries a null ordering value.
That null then reaches `BufferedRecordMergerFactory.shouldKeepNewerRecord`,
which calls `getOrderingValue().compareTo(...)` without a null guard. During a
partition-path update index merge
(`HoodieIndexUtils.mergeForPartitionUpdatesAndDeletionsIfNeeded` ->
`EventTimeRecordMerger.finalMerge` -> `shouldKeepNewerRecord`) this throws:
```
java.lang.NullPointerException
at
org.apache.hudi.common.table.read.BufferedRecordMergerFactory.shouldKeepNewerRecord(...)
```
A nullable ordering column is common in practice (for example a nullable
BIGINT event-time column), so any MOR table with such a column can hit this on
reads/merges.
## Secondary issue
Coercing the null ordering value to the default
(`HoodieRecord.DEFAULT_ORDERING_VALUE`, an `Integer 0`) is not sufficient on
its own: `shouldKeepNewerRecord` and `EventTimePartialRecordMerger.finalMerge`
then compare that `Integer 0` against a real `Long` ordering value and throw
`ClassCastException: java.lang.Long cannot be cast to java.lang.Integer`. Both
comparison sites need an `isSameClass` guard (as `deltaMergeDeleteRecord`
already has) so a default/type-mismatched ordering value is treated as a tie
rather than compared directly.
## Expected behavior
A null ordering field value should not crash reads or merges. It should be
treated as the default ordering value, and ordering comparisons should be
skipped (record treated as a tie, newer kept) when either value is the default
or the two values are of different types.
## Environment
- Affects the 1.x line (file group reader / `BufferedRecordMergerFactory`).
- Merge mode: `EVENT_TIME_ORDERING` (and the partial-update variant when
`hoodie.partial.update.mode` is set).
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