nbauernfeind opened a new issue, #471:
URL: https://github.com/apache/arrow-java/issues/471
### Describe the bug, including details regarding any error messages,
version, and platform.
`ListViewVector`'s `#copyFrom` is broken. Here is a test (that otherwise
works for `List`):
```java
@Test
public void testListViewCopy() {
final Field childField = new Field("testChild",
new FieldType(false, new ArrowType.Int(32, true), null),
null);
final Field listField = new Field("test",
new FieldType(false, ArrowType.ListView.INSTANCE, null),
Collections.singletonList(childField));
try (final ListViewVector src = (ListViewVector)
listField.createVector(allocator);
final ListViewVector dst = (ListViewVector)
listField.createVector(allocator)) {
// init child vector
final int numValues = 10;
final IntVector childSrc = (IntVector) src.getDataVector();
childSrc.setValueCount(numValues);
for (int ii = 0; ii < numValues; ++ii) {
childSrc.set(ii, ii);
}
// init source vector
src.setValueCount(1);
src.startNewValue(0);
src.endValue(0, numValues);
assertEquals(List.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9),
src.getObject(0));
dst.setValueCount(src.getValueCount());
dst.getDataVector().setValueCount(numValues);
dst.copyFrom(0, 0, src);
assertEquals(src.getObject(0), dst.getObject(0));
}
}
```
`ComplexCopier#writeValue` has impl:
```java
case LIST:
case LISTVIEW:
case LARGELIST:
case LARGELISTVIEW:
case FIXED_SIZE_LIST:
if (reader.isSet()) {
writer.startList();
while (reader.next()) {
FieldReader childReader = reader.reader();
FieldWriter childWriter = getListWriterForReader(childReader,
writer);
if (childReader.isSet()) {
writeValue(childReader, childWriter);
} else {
childWriter.writeNull();
}
}
writer.endList();
} else {
writer.writeNull();
}
break;
```
Note that the implementation of `UnionListViewReader#next` will never ever
return false:
```java
@Override
public boolean next() {
// Here, the currentOffSet keeps track of the current position in the
vector inside the list at
// set position.
// And, size keeps track of the elements count in the list, so to make
sure we traverse
// the full list, we need to check if the currentOffset is less than the
currentOffset + size
if (currentOffset < currentOffset + size) {
data.getReader().setPosition(currentOffset++);
return true;
} else {
return false;
}
}
```
Notice how `currentOffset < currentOffset + size` can only ever be false if
`size <= 0` -- but `size` is never modified.
I suspect the desired conditional is:
```
if (currentOffset < size) {
```
Please note that the embedded comment is also nonsense. It's not clear why
the approach differs from `UnionListReader`, keeping a consistent approach
would have prevented introducing a bug.
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