mikemccand commented on a change in pull request #815: LUCENE-8213: Introduce
Asynchronous Caching in LRUQueryCache
URL: https://github.com/apache/lucene-solr/pull/815#discussion_r326565568
##########
File path: lucene/core/src/java/org/apache/lucene/search/LRUQueryCache.java
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@@ -832,5 +894,25 @@ public BulkScorer bulkScorer(LeafReaderContext context)
throws IOException {
return new DefaultBulkScorer(new ConstantScoreScorer(this, 0f,
ScoreMode.COMPLETE_NO_SCORES, disi));
}
+ // Perform a cache load asynchronously
+ private void cacheAsynchronously(LeafReaderContext context,
IndexReader.CacheHelper cacheHelper) throws IOException {
+ FutureTask<Void> task = new FutureTask<>(() -> {
+ DocIdSet localDocIdSet = cache(context);
+ putIfAbsent(in.getQuery(), localDocIdSet, cacheHelper);
+
+ //remove the key from inflight -- the key is loaded now
+ inFlightAsyncLoadQueries.remove(in.getQuery());
+ return null;
+ });
+ /*
+ * If the current query is already being asynchronously cached,
+ * do not trigger another cache operation
+ */
+ if (inFlightAsyncLoadQueries.contains(in.getQuery())) {
+ return;
+ }
+ inFlightAsyncLoadQueries.add(in.getQuery());
Review comment:
Hmm still a concurrency bug here, allowing two threads to cache the same
query -- instead of separate `.contains` and `.add` calls, can you simply call
`.add` and look at its return value to decide whether you should in fact cache?
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