add a marker CachedFilter

this allows to easily and globally check if we cache a filter or not, all filter caching uses this marker interface

src/main/java/org/elasticsearch/common/lucene/search/CachedFilter.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to ElasticSearch and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.common.lucene.search;
+
+import org.apache.lucene.search.Filter;
+
+/**
+ * A marker indicating that this is a cached filter.
+ */
+public abstract class CachedFilter extends Filter {
+
+    public static boolean isCached(Filter filter) {
+        return filter instanceof CachedFilter;
+    }
+}

src/main/java/org/elasticsearch/index/cache/filter/FilterCache.java

@@ -43,8 +43,6 @@ public interface FilterCache extends IndexComponent, CloseableComponent {
 
     Filter cache(Filter filterToCache);
 
-    boolean isCached(Filter filter);
-
     void clear(IndexReader reader);
 
     void clear(String reason);

src/main/java/org/elasticsearch/index/cache/filter/none/NoneFilterCache.java

@@ -54,11 +54,6 @@ public class NoneFilterCache extends AbstractIndexComponent implements FilterCac
         return filterToCache;
     }
 
-    @Override
-    public boolean isCached(Filter filter) {
-        return false;
-    }
-
     @Override
     public void clear(String reason) {
         // nothing to do here

src/main/java/org/elasticsearch/index/cache/filter/weighted/WeightedFilterCache.java

@@ -33,6 +33,7 @@ import org.apache.lucene.util.FixedBitSet;
 import org.elasticsearch.ElasticSearchException;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.lucene.docset.DocIdSets;
+import org.elasticsearch.common.lucene.search.CachedFilter;
 import org.elasticsearch.common.lucene.search.NoCacheFilter;
 import org.elasticsearch.common.metrics.CounterMetric;
 import org.elasticsearch.common.metrics.MeanMetric;
@@ -122,18 +123,13 @@ public class WeightedFilterCache extends AbstractIndexComponent implements Filte
         if (filterToCache instanceof NoCacheFilter) {
             return filterToCache;
         }
-        if (isCached(filterToCache)) {
+        if (CachedFilter.isCached(filterToCache)) {
             return filterToCache;
         }
         return new FilterCacheFilterWrapper(filterToCache, this);
     }
 
-    @Override
-    public boolean isCached(Filter filter) {
-        return filter instanceof FilterCacheFilterWrapper;
-    }
-
-    static class FilterCacheFilterWrapper extends Filter {
+    static class FilterCacheFilterWrapper extends CachedFilter {
 
         private final Filter filter;