pkolaczk commented on code in PR #3054:
URL: https://github.com/apache/cassandra/pull/3054#discussion_r1466706005
##########
src/java/org/apache/cassandra/index/sai/iterators/KeyRangeIntersectionIterator.java:
##########
@@ -77,7 +77,19 @@ protected PrimaryKey computeNext()
if (index != alreadyAvanced)
{
KeyRangeIterator range = ranges.get(index);
- PrimaryKey nextKey = nextOrNull(range, highestKey);
+ PrimaryKey nextKey = range.getCurrent();
+
+ // Note that we will either have a data model that
produces SKINNY primary keys or a data model
+ // that produces some combination of WIDE and STATIC
prikary keys.
+ if (nextKey.kind() == PrimaryKey.Kind.WIDE ||
nextKey.kind() == highestKey.kind())
+ // We can always skip if the target is of the same
kind or this range is non-static.
+ nextKey = nextOrNull(range, highestKey);
+ else if (nextKey.kind() == PrimaryKey.Kind.STATIC &&
nextKey.compareTo(highestKey) < 0)
+ // For a range of static keys, only skip if we'e
advanced to a new partition, and when we
+ // do, skip to an actual static key. We may otherwise
skip too far, as static row IDs always
+ // precede non-static ones in on-disk postings lists.
+ nextKey = nextOrNull(range, highestKey.toStatic());
Review Comment:
It is not very obvious to me it always terminates. This `if / else if` has a
theoretical path where it does *not* advance the range at all. Let's assume the
first range returns a SKINNY key and the second range returns only STATIC keys
then I guess the first range might get stuck because neither condition would be
ever true.
Im also not sure if now this invariant of the for loop in line 75 still
holds:
```
// Once this inner loop finishes normally, all iterators are guaranteed to
be at the same value.
```
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