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Objects: don't recreate iterators when initializing in MergingKvIterator

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This commit is contained in:
Stepan Usatiuk
2025-03-12 21:21:10 +01:00
parent 5c905379ae
commit 1d22465e4a
1 changed files with 28 additions and 39 deletions
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67
dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/MergingKvIterator.java
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@@ -16,58 +16,47 @@ public class MergingKvIterator<K extends Comparable<K>, V> extends ReversibleKvI
_goingForward = true;
_name = name;
IteratorStart initialStartType = startType;
K initialStartKey = startKey;
boolean fail = false;
{
int counter = 0;
var iteratorsTmp = new HashMap<CloseableKvIterator<K, V>, Integer>();
for (var iteratorFn : iterators) {
var iterator = iteratorFn.get(startType, startKey);
iteratorsTmp.put(iterator, counter++);
}
_iterators = Map.copyOf(iteratorsTmp);
}
if (startType == IteratorStart.LT || startType == IteratorStart.LE) {
// Starting at a greatest key less than/less or equal than:
// We have a bunch of iterators that have given us theirs "greatest LT/LE key"
// now we need to pick the greatest of those to start with
// But if some of them don't have a lesser key, we need to pick the smallest of those
var initialIterators = iterators.stream().map(p -> p.get(initialStartType, initialStartKey)).toList();
try {
IteratorStart finalStartType = startType;
var found = initialIterators.stream()
.filter(CloseableKvIterator::hasNext)
.map((i) -> {
var peeked = i.peekNextKey();
var found = _iterators.keySet().stream()
.filter(CloseableKvIterator::hasNext)
.map((i) -> {
var peeked = i.peekNextKey();
// Log.warnv("peeked: {0}, from {1}", peeked, i.getClass());
return peeked;
}).distinct().collect(Collectors.partitioningBy(e -> finalStartType == IteratorStart.LE ? e.compareTo(initialStartKey) <= 0 : e.compareTo(initialStartKey) < 0));
K initialMaxValue;
if (!found.get(true).isEmpty())
initialMaxValue = found.get(true).stream().max(Comparator.naturalOrder()).orElse(null);
else
initialMaxValue = found.get(false).stream().min(Comparator.naturalOrder()).orElse(null);
if (initialMaxValue == null) {
fail = true;
return peeked;
}).distinct().collect(Collectors.partitioningBy(e -> startType == IteratorStart.LE ? e.compareTo(startKey) <= 0 : e.compareTo(startKey) < 0));
K initialMaxValue;
if (!found.get(true).isEmpty())
initialMaxValue = found.get(true).stream().max(Comparator.naturalOrder()).orElse(null);
else
initialMaxValue = found.get(false).stream().min(Comparator.naturalOrder()).orElse(null);
for (var iterator : _iterators.keySet()) {
while (iterator.hasNext() && iterator.peekNextKey().compareTo(initialMaxValue) < 0) {
iterator.skip();
}
startKey = initialMaxValue;
startType = IteratorStart.GE;
} finally {
initialIterators.forEach(CloseableKvIterator::close);
}
}
if (fail) {
_iterators = Map.of();
return;
}
int counter = 0;
var iteratorsTmp = new HashMap<CloseableKvIterator<K, V>, Integer>();
for (var iteratorFn : iterators) {
var iterator = iteratorFn.get(startType, startKey);
iteratorsTmp.put(iterator, counter++);
}
_iterators = Map.copyOf(iteratorsTmp);
for (CloseableKvIterator<K, V> iterator : _iterators.keySet()) {
advanceIterator(iterator);
}
Log.tracev("{0} Created: {1}", _name, _sortedIterators);
switch (initialStartType) {
switch (startType) {
// case LT -> {
// assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(initialStartKey) < 0;
// }
@@ -75,10 +64,10 @@ public class MergingKvIterator<K extends Comparable<K>, V> extends ReversibleKvI
// assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(initialStartKey) <= 0;
// }
case GT -> {
assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(initialStartKey) > 0;
assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(startKey) > 0;
}
case GE -> {
assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(initialStartKey) >= 0;
assert _sortedIterators.isEmpty() || _sortedIterators.firstKey().compareTo(startKey) >= 0;
}
}
}