Ruiqi Dong created COLLECTIONS-889:
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Summary: `IndexedCollection.remove()` clears the whole key bucket
in non-unique indexes
Key: COLLECTIONS-889
URL: https://issues.apache.org/jira/browse/COLLECTIONS-889
Project: Commons Collections
Issue Type: Bug
Components: Collection
Reporter: Ruiqi Dong
*Summary*
For non-unique indexes, multiple collection elements may share the same
transformed key. The current `remove(...)` implementation removes the object
from the decorated collection correctly, but then removes the entire key from
the index. That drops the remaining same-key elements from the index even
though they are still present in the collection.
*Affected code*
File:
`src/main/java/org/apache/commons/collections4/collection/IndexedCollection.java`
{code:java}
@SuppressWarnings("unchecked")
@Override
public boolean remove(final Object object) {
final boolean removed = super.remove(object);
if (removed) {
removeFromIndex((C) object);
}
return removed;
}
private void removeFromIndex(final C object) {
index.remove(keyTransformer.apply(object));
} {code}
*Reproducer*
Add the following test to
`src/test/java/org/apache/commons/collections4/collection/IndexedCollectionTest.java`
{code:java}
@Test
void testRemovePreservesRemainingValuesWithSameTransformedKey() {
final IndexedCollection<Integer, String> indexed =
(IndexedCollection<Integer, String>) decorateCollection(new
ArrayList<>());
indexed.add("01");
indexed.add("1");
indexed.remove("01");
assertEquals("1", indexed.get(1));
assertNotNull(indexed.values(1));
assertEquals(asList("1"), new ArrayList<>(indexed.values(1)));
} {code}
Run:
{code:java}
mvn -q
-Dtest=org.apache.commons.collections4.collection.IndexedCollectionTest#testRemovePreservesRemainingValuesWithSameTransformedKey
test {code}
Observed behavior:
`get(1)` returns `null` even though `"1"` is still present in the decorated
collection.
{code:java}
expected: <1> but was: <null> {code}
Expected behavior:
Removing `"01"` should leave the other same-key value `"1"` indexed and
retrievable.
In the non-unique configuration, the index is supposed to track all values that
share a key. Removing one value should only remove that single value from the
index entry, not delete the whole key bucket. The current implementation leaves
the collection and the index out of sync after a normal successful
`remove(...)`.
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