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Honor set-multimap hash-collision node invariant during removals #42

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Merged
msteindorfer merged 2 commits into from
Jan 23, 2026
Merged

Honor set-multimap hash-collision node invariant during removals #42

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c4c32d9
Assert set-multimap hash-collision node invariant
msteindorfer Jan 22, 2026
abcf9f8
Honor set-multimap hash-collision node invariant during removals
msteindorfer Jan 23, 2026
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50 changes: 43 additions & 7 deletions src/main/java/io/usethesource/capsule/core/PersistentTrieSetMultimap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2223,6 +2223,8 @@ private static final class HashCollisionNode<K, V> extends AbstractHashCollision
final List<Map.Entry<K, io.usethesource.capsule.Set.Immutable<V>>> collisionContent) {
this.hash = hash;
this.collisionContent = collisionContent;

assert this.collisionContent.size() >= 2;
}

@Override
Expand Down Expand Up @@ -2652,8 +2654,24 @@ public AbstractSetMultimapNode<K, V> removed(AtomicReference<Thread> mutator, K
.filter(kImmutableSetEntry -> kImmutableSetEntry != optionalTuple.get())
.collect(Collectors.toList());

details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE));
return new HashCollisionNode<K, V>(hash, updatedCollisionContent);
if (updatedCollisionContent.size() == 1) {
/*
* Create a root node that stores data for the single remaining key. This node will a) either become the
* new root returned, or b) unwrapped and inlined on the path upwards.
*/
Map.Entry<K, io.usethesource.capsule.Set.Immutable<V>> remainingEntry = updatedCollisionContent.get(0);

K remainingKey = remainingEntry.getKey();
// Passing the `remainingValues` set as an argument to `MultimapNode#inserted`. The method ensures to unbox
// singleton sets, hence we do not have to deal with the case distinction between 1:1 and 1:n mappings here.
io.usethesource.capsule.Set.Immutable<V> remainingValues = remainingEntry.getValue();

details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE));
return CompactSetMultimapNode.<K, V>nodeOf(null).inserted(null, remainingKey, remainingValues, keyHash, 0, MultimapResult.unchanged());
} else {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE));
return new HashCollisionNode<K, V>(hash, updatedCollisionContent);
}
} else {
Function<Map.Entry<K, io.usethesource.capsule.Set.Immutable<V>>, Map.Entry<K, io.usethesource.capsule.Set.Immutable<V>>> substitutionMapper =
(kImmutableSetEntry) -> {
Expand Down Expand Up @@ -2698,12 +2716,30 @@ public AbstractSetMultimapNode<K, V> removed(AtomicReference<Thread> mutator, K
.filter(kImmutableSetEntry -> kImmutableSetEntry != optionalTuple.get())
.collect(Collectors.toList());

if (values.size() == 1) {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE), values);
return new HashCollisionNode<K, V>(hash, updatedCollisionContent);
if (updatedCollisionContent.size() == 1) {
/*
* Create a root node that stores data for the single remaining key. This node will a) either become the
* new root returned, or b) unwrapped and inlined on the path upwards.
*/
Map.Entry<K, io.usethesource.capsule.Set.Immutable<V>> remainingEntry = updatedCollisionContent.get(0);

K remainingKey = remainingEntry.getKey();
// Passing the `remainingValues` set as an argument to `MultimapNode#inserted`. The method ensures to unbox
// singleton sets, hence we do not have to deal with the case distinction between 1:1 and 1:n mappings here.
io.usethesource.capsule.Set.Immutable<V> remainingValues = remainingEntry.getValue();

if (values.size() == 1) {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE), values);
} else {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE_COLLECTION), values);
}
return CompactSetMultimapNode.<K, V>nodeOf(null).inserted(null, remainingKey, remainingValues, keyHash, 0, MultimapResult.unchanged());
} else {
details
.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE_COLLECTION), values);
if (values.size() == 1) {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE), values);
} else {
details.modified(REMOVED_PAYLOAD, MultimapResult.Modification.flag(REMOVED_KEY, REMOVED_VALUE_COLLECTION), values);
}
return new HashCollisionNode<K, V>(hash, updatedCollisionContent);
}
}
Expand Down