solr-cache-add-keyset.patch

diff --git a/solr/core/src/java/org/apache/solr/search/CaffeineCache.java b/solr/core/src/java/org/apache/solr/search/CaffeineCache.java
index f18248669ba..b608a00c12d 100644
--- a/solr/core/src/java/org/apache/solr/search/CaffeineCache.java
+++ b/solr/core/src/java/org/apache/solr/search/CaffeineCache.java
@@ -35,9 +35,6 @@ import java.util.concurrent.ForkJoinPool;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.LongAdder;
 
-import com.github.benmanes.caffeine.cache.AsyncCache;
-import com.github.benmanes.caffeine.cache.RemovalCause;
-import com.github.benmanes.caffeine.cache.RemovalListener;
 import org.apache.lucene.util.Accountable;
 import org.apache.lucene.util.RamUsageEstimator;
 import org.apache.solr.common.SolrException;
@@ -47,9 +44,12 @@ import org.apache.solr.util.IOFunction;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.github.benmanes.caffeine.cache.AsyncCache;
 import com.github.benmanes.caffeine.cache.Cache;
 import com.github.benmanes.caffeine.cache.Caffeine;
 import com.github.benmanes.caffeine.cache.Policy.Eviction;
+import com.github.benmanes.caffeine.cache.RemovalCause;
+import com.github.benmanes.caffeine.cache.RemovalListener;
 import com.github.benmanes.caffeine.cache.stats.CacheStats;
 import com.google.common.annotations.VisibleForTesting;
 
@@ -291,6 +291,11 @@ public class CaffeineCache<K, V> extends SolrCacheBase implements SolrCache<K, V
     return existing;
   }
 
+  @Override
+  public Set<K> keySet() {
+    return cache.asMap().keySet();
+  }
+
   @Override
   public void clear() {
     cache.invalidateAll();
diff --git a/solr/core/src/java/org/apache/solr/search/FastLRUCache.java b/solr/core/src/java/org/apache/solr/search/FastLRUCache.java
index bf3b01049e0..c891932d1cd 100644
--- a/solr/core/src/java/org/apache/solr/search/FastLRUCache.java
+++ b/solr/core/src/java/org/apache/solr/search/FastLRUCache.java
@@ -249,6 +249,12 @@ public class FastLRUCache<K, V> extends SolrCacheBase implements SolrCache<K, V>
     return cache.remove(key);
   }
 
+  @SuppressWarnings("unchecked")
+  @Override
+  public Set<K> keySet() {
+    return (Set<K>) cache.getMap().keySet();
+  }
+
   @Override
   public V get(K key) {
     return cache.get(key);
diff --git a/solr/core/src/java/org/apache/solr/search/LFUCache.java b/solr/core/src/java/org/apache/solr/search/LFUCache.java
index fa5be4360f4..242ea454538 100644
--- a/solr/core/src/java/org/apache/solr/search/LFUCache.java
+++ b/solr/core/src/java/org/apache/solr/search/LFUCache.java
@@ -189,6 +189,12 @@ public class LFUCache<K, V> implements SolrCache<K, V>, Accountable {
     return cache.remove(key);
   }
 
+  @SuppressWarnings("unchecked")
+  @Override
+  public Set<K> keySet() {
+    return (Set<K>) cache.getMap().keySet();
+  }
+
   @Override
   public V computeIfAbsent(K key, IOFunction<? super K, ? extends V> mappingFunction) {
     return cache.computeIfAbsent(key, k -> {
diff --git a/solr/core/src/java/org/apache/solr/search/LRUCache.java b/solr/core/src/java/org/apache/solr/search/LRUCache.java
index cb2de0d6e9d..cf3ba08ff1d 100644
--- a/solr/core/src/java/org/apache/solr/search/LRUCache.java
+++ b/solr/core/src/java/org/apache/solr/search/LRUCache.java
@@ -329,6 +329,11 @@ public class LRUCache<K,V> extends SolrCacheBase implements SolrCache<K,V>, Acco
     }
   }
 
+  @Override
+  public Set<K> keySet() {
+    return map.keySet();
+  }
+
   @Override
   public V put(K key, V value) {
     if (maxSize == Integer.MAX_VALUE && maxRamBytes == Long.MAX_VALUE) {
diff --git a/solr/core/src/java/org/apache/solr/search/SolrCache.java b/solr/core/src/java/org/apache/solr/search/SolrCache.java
index 012c6a09b48..5b02e4f09fa 100644
--- a/solr/core/src/java/org/apache/solr/search/SolrCache.java
+++ b/solr/core/src/java/org/apache/solr/search/SolrCache.java
@@ -16,14 +16,15 @@
  */
 package org.apache.solr.search;
 
-import org.apache.solr.core.SolrInfoBean;
-import org.apache.solr.metrics.SolrMetricProducer;
-import org.apache.solr.util.IOFunction;
-
 import java.io.IOException;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Function;
 
+import org.apache.solr.core.SolrInfoBean;
+import org.apache.solr.metrics.SolrMetricProducer;
+import org.apache.solr.util.IOFunction;
+
 
 /**
  * Primary API for dealing with Solr's internal caches.
@@ -100,6 +101,8 @@ public interface SolrCache<K,V> extends SolrInfoBean, SolrMetricProducer {
 
   public V remove(K key);
 
+  public Set<K> keySet();
+
   /**
    * Get an existing element or atomically compute it if missing.
    * @param key key