Enhanced the close() method with defensive null checks to prevent NullPointerException during resource cleanup

[Akanksha-kedia]

File Modified: FixedByteSingleValueMultiColumnReaderWriter.java

Location: pinot-segment-local/src/main/java/org/apache/pinot/segment/local/io/readerwriter/impl/FixedByteSingleValueMultiColumnReaderWriter.java

Improvement: Enhanced the close() method with defensive null checks to prevent NullPointerException during resource cleanup.

Before:

@Override
public void close() throws IOException {
  for (FixedByteSingleValueMultiColWriter writer : _writers) {
    writer.close();
  }
  for (FixedByteSingleValueMultiColReader reader : _readers) {
    reader.close();
  }
}

After:

@Override
public void close() throws IOException {
  if (_writers != null) {
    for (FixedByteSingleValueMultiColWriter writer : _writers) {
      if (writer != null) {
        writer.close();
      }
    }
  }
  if (_readers != null) {
    for (FixedByteSingleValueMultiColReader reader : _readers) {
      if (reader != null) {
        reader.close();
      }
    }
  }
}

Impact

✅ Prevents NullPointerException during resource cleanup
✅ Improves robustness of the close() method
✅ Follows defensive programming best practices
✅ No functional changes to normal operation
✅ Low risk - purely defensive improvement

[Akanksha-kedia]

@xiangfu0 please review

[codecov-commenter]

Codecov Report

❌ Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.21%. Comparing base (eb4c342) to head (c016bbf).

Files with missing lines	Patch %	Lines
...l/FixedByteSingleValueMultiColumnReaderWriter.java	60.00%	0 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #17110      +/-   ##
============================================
- Coverage     63.24%   63.21%   -0.03%     
  Complexity     1428     1428              
============================================
  Files          3104     3104              
  Lines        183423   183427       +4     
  Branches      28112    28116       +4     
============================================
- Hits         116010   115961      -49     
- Misses        58442    58501      +59     
+ Partials       8971     8965       -6     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-11	63.18% <60.00%> (-0.01%)	⬇️
java-21	63.18% <60.00%> (-0.01%)	⬇️
temurin	63.21% <60.00%> (-0.03%)	⬇️
unittests	63.21% <60.00%> (-0.03%)	⬇️
unittests1	56.24% <0.00%> (+0.01%)	⬆️
unittests2	33.60% <60.00%> (-0.05%)	⬇️

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[yashmayya]

Why is this change needed? When can the readers or writers be null?