Ruiqi Dong created CALCITE-7556:
-----------------------------------
Summary: NameMultimap.remove(key, value) leaves an empty key
bucket behind
Key: CALCITE-7556
URL: https://issues.apache.org/jira/browse/CALCITE-7556
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.41.0
Reporter: Ruiqi Dong
*Summary*
NameMultimap.remove(String, V) removes the value from the per-key list, but if
that value was the last entry for the key, it does not remove the key itself
from the backing NameMap. The object is left in an inconsistent state:
* range(key, ...) is empty
* containsKey(key, ...) is still true
* map() still contains the key with an empty list
Although remove is marked @Experimental, the surrounding public API still
exposes clear consistency expectations between remove, containsKey, range, and
map. The current behavior breaks those expectations.
*Affected code*
File: core/src/main/java/org/apache/calcite/util/NameMultimap.java
{code:java}
@Experimental
public boolean remove(String key, V value) {
final List<V> list = map().get(key);
if (list == null) {
return false;
}
return list.remove(value);
} {code}
*Reproducer*Add the following test to
core/src/test/java/org/apache/calcite/util/UtilTest.java
{code:java}
@Test void testNameMultimapRemoveLastValueRemovesKey() {
final NameMultimap<Integer> map = new NameMultimap<>();
map.put("baz", 1);
assertTrue(map.remove("baz", 1));
assertThat(map.range("baz", true), hasSize(0));
assertThat(map.containsKey("baz", true), is(false));
assertThat(map.containsKey("BAZ", false), is(false));
assertThat(map.map(), aMapWithSize(0));
} {code}
Run:
{code:java}
./gradlew :core:test \
--tests
org.apache.calcite.util.UtilTest.testNameMultimapRemoveLastValueRemovesKey
{code}
Observed behavior:
The key remains visible after the last value has been removed
{code:java}
Expected: is <false>
but: was <true> {code}
The failure is triggered by
{code:java}
assertThat(map.containsKey("baz", true), is(false)); {code}
Expected behavior:
After removing the last value associated with a key, the multimap should no
longer report that key as present.
This is a container state-consistency bug. The public query methods disagree
about whether the key still exists, and the backing map retains an empty bucket
that should have been deleted. The @Experimental annotation may lower
compatibility expectations, but it does not make mutually inconsistent
observable state acceptable.
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