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Avoid allocations in DataLoaderHelper.dispatch when there's no work #136

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Merged
merged 1 commit into from
Nov 14, 2023
Merged

Avoid allocations in DataLoaderHelper.dispatch when there's no work #136

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30 changes: 23 additions & 7 deletions src/main/java/org/dataloader/DataLoaderHelper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -162,12 +162,21 @@ Object getCacheKeyWithContext(K key, Object context) {

DispatchResult<V> dispatch() {
boolean batchingEnabled = loaderOptions.batchingEnabled();
//
// we copy the pre-loaded set of futures ready for dispatch
final List<K> keys = new ArrayList<>();
final List<Object> callContexts = new ArrayList<>();
final List<CompletableFuture<V>> queuedFutures = new ArrayList<>();
final List<K> keys;
final List<Object> callContexts;
final List<CompletableFuture<V>> queuedFutures;
synchronized (dataLoader) {
int queueSize = loaderQueue.size();
if (queueSize == 0) {
lastDispatchTime.set(now());
return emptyDispatchResult();
}

// we copy the pre-loaded set of futures ready for dispatch
keys = new ArrayList<>(queueSize);
callContexts = new ArrayList<>(queueSize);
queuedFutures = new ArrayList<>(queueSize);

loaderQueue.forEach(entry -> {
keys.add(entry.getKey());
queuedFutures.add(entry.getValue());
Expand All @@ -176,8 +185,8 @@ DispatchResult<V> dispatch() {
loaderQueue.clear();
lastDispatchTime.set(now());
}
if (!batchingEnabled || keys.isEmpty()) {
return new DispatchResult<>(completedFuture(emptyList()), 0);
if (!batchingEnabled) {
return emptyDispatchResult();
}
final int totalEntriesHandled = keys.size();
//
Expand Down Expand Up @@ -524,4 +533,11 @@ private CompletableFuture<List<V>> setToValueCache(List<V> assembledValues, List
}
return CompletableFuture.completedFuture(assembledValues);
}

private static final DispatchResult<?> EMPTY_DISPATCH_RESULT = new DispatchResult<>(completedFuture(emptyList()), 0);

@SuppressWarnings("unchecked") // Casting to any type is safe since the underlying list is empty
private static <T> DispatchResult<T> emptyDispatchResult() {
return (DispatchResult<T>) EMPTY_DISPATCH_RESULT;
}
}