acrites commented on code in PR #40750:
URL: https://github.com/apache/beam/pull/40750#discussion_r4391873031
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runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/windmill/state/WindmillMapViaMultimap.java:
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@@ -62,19 +62,26 @@ public void put(KeyT key, ValueT value) {
multimap.put(key, value);
}
+ @SuppressWarnings("nullness")
@Override
public ReadableState<ValueT> computeIfAbsent(
KeyT key, Function<? super KeyT, ? extends ValueT> mappingFunction) {
// Note that computeIfAbsent comments indicate that the read is lazy but
this matches the
- // existing eager
- // behavior of WindmillMap.
+ // existing eager behavior of WindmillMap.
Iterable<ValueT> existingValues = multimap.get(key).read();
- if (Iterables.isEmpty(existingValues)) {
+ Iterator<ValueT> iterator = existingValues.iterator();
+ if (!iterator.hasNext()) {
ValueT inserted = mappingFunction.apply(key);
multimap.put(key, inserted);
return ReadableStates.immediate(inserted);
} else {
- return
ReadableStates.immediate(Iterables.getOnlyElement(existingValues));
+ ValueT existing = Iterators.getOnlyElement(iterator);
+ if (existing == null) {
Review Comment:
In all of these cases the behavior seems to be "if the value is currently
mapped to null, apply the mapping function and overwrite it with whatever the
mapping function returns". I think they all return the previous value that was
stored in the map. So it seems like `WindmillMapViaMultimap` is the only class
not implementing `computeIfAbsent` based on the original comments.
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