DX-122953 Preserve offset bytes when expanding empty buffers

Author: prashanthbdremio

vector/src/main/java/org/apache/arrow/vector/complex/LargeListVector.java

@@ -326,6 +326,8 @@ private void ensureEmptyOffsetBufferCapacity(long requiredCapacity) {
     long previousOffsetAllocationSizeInBytes = offsetAllocationSizeInBytes;
     ArrowBuf oldOffsetBuffer = offsetBuffer;
     offsetBuffer = allocateOffsetBuffer(requiredCapacity);
+    offsetBuffer.setBytes(
+        0, oldOffsetBuffer, 0, Math.min(oldOffsetBuffer.capacity(), requiredCapacity));
     offsetAllocationSizeInBytes = previousOffsetAllocationSizeInBytes;
     oldOffsetBuffer.getReferenceManager().release();
   }

vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java

@@ -284,6 +284,8 @@ private void ensureEmptyOffsetBufferCapacity(long requiredCapacity) {
     long previousOffsetAllocationSizeInBytes = offsetAllocationSizeInBytes;
     ArrowBuf oldOffsetBuffer = offsetBuffer;
     offsetBuffer = allocateOffsetBuffer(requiredCapacity);
+    offsetBuffer.setBytes(
+        0, oldOffsetBuffer, 0, Math.min(oldOffsetBuffer.capacity(), requiredCapacity));
     offsetAllocationSizeInBytes = previousOffsetAllocationSizeInBytes;
     oldOffsetBuffer.getReferenceManager().release();
   }