mikemccand commented on code in PR #11780:
URL: https://github.com/apache/lucene/pull/11780#discussion_r982553986
##########
lucene/core/src/java/org/apache/lucene/search/ReferenceManager.java:
##########
@@ -219,6 +219,36 @@ public final boolean maybeRefresh() throws IOException {
return doTryRefresh;
}
+ /** Compute some state of the reference using a parameter. */
+ @FunctionalInterface
+ public interface StateCalculator<R, G, P> {
+ R calculate(G current, P param);
+ }
+
+ /**
+ * If you need to compute something after the refresh, you can use this
method instead of {@link
+ * #maybeRefresh()}.
+ *
+ * @throws IOException if refreshing the resource causes an {@link
IOException}
+ */
+ public final <R, P> R maybeRefreshAndReturnState(
+ StateCalculator<R, G, P> refreshedStateCalculator, P param) throws
IOException {
+ ensureOpen();
+
+ // Ensure only 1 thread does refresh at once; other threads just return
immediately:
+ final boolean doTryRefresh = refreshLock.tryLock();
+ if (doTryRefresh) {
+ try {
+ doMaybeRefresh();
+ return refreshedStateCalculator.calculate(current, param);
Review Comment:
Hmm why is it necessary to compute this state under lock? Can't the caller
just compute the state themselves when they get the refreshed reader?
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