maedhroz commented on PR #4900:
URL: https://github.com/apache/cassandra/pull/4900#issuecomment-4791824207
For finding 1 above, this test does appear to fail, but I could still just
be testing the wrong thing...
```
/**
* Verifies that re-inserting every key that already exists reports a net
heap delta of exactly zero,
* and that {@code onAllocatedOnHeap} is actually invoked (not silently
skipped by an {@code allocated > 0}
* guard). The call must happen so that callers accumulating signed deltas
see the confirmation, and so
* that a negative allocated value cannot permanently disable accounting by
crossing the -1 sentinel.
*/
@Test
public void netZeroDeltaOnAllocatedOnHeapIsInvoked()
{
int numKeys = BTree.MAX_KEYS * BTree.MAX_KEYS;
Integer[] keys = new Integer[numKeys];
for (int i = 0; i < numKeys; i++)
keys[i] = i;
Object[] tree = BTree.build(BulkIterator.of(keys), numKeys,
UpdateFunction.noOp());
Object[] insert = BTree.build(BulkIterator.of(keys), numKeys,
UpdateFunction.noOp());
// Use a counting variant that records invocation count separately from
the accumulated total
final long[] invocations = { 0 };
final long[] total = { 0 };
UpdateFunction<Integer, Integer> fn = new UpdateFunction<Integer,
Integer>()
{
@Override public Integer insert(Integer i) { return i; }
@Override public Integer merge(Integer existing, Integer update) {
return update; }
@Override public void onAllocatedOnHeap(long delta)
{
invocations[0]++;
total[0] += delta;
}
};
Object[] result = BTree.update(tree, insert, CMP, fn);
assertSame("full re-insert of identical keys must reuse the existing
tree root", tree, result);
assertEquals("reported net delta must be zero for a full re-insert of
identical keys",
0L, total[0]);
// This is the assertion that catches the bug:
// with `if (allocated > 0)`, invocations[0] == 0 (call skipped entirely)
// with `if (allocated != 0)` or unconditional, invocations[0] == 1
assertTrue("onAllocatedOnHeap must be invoked even for a net-zero
update; " +
"skipping it conflates 'tracking disabled' (-1 sentinel) with
'net zero result' (0)",
invocations[0] >= 1);
}
```
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