Remove PROTOTYPE from KeyedFilter

Relates to #17085

core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/FiltersAggregator.java

@@ -58,8 +58,6 @@ public class FiltersAggregator extends BucketsAggregator {
     public static final ParseField OTHER_BUCKET_KEY_FIELD = new ParseField("other_bucket_key");
 
     public static class KeyedFilter implements Writeable<KeyedFilter>, ToXContent {
-
-        static final KeyedFilter PROTOTYPE = new KeyedFilter("", new MatchAllQueryBuilder());
         private final String key;
         private final QueryBuilder<?> filter;
 
@@ -78,6 +76,20 @@ public class FiltersAggregator extends BucketsAggregator {
             }
         }
 
+        /**
+         * Read from a stream.
+         */
+        public KeyedFilter(StreamInput in) throws IOException {
+            key = in.readString();
+            filter = in.readQuery();
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            out.writeString(key);
+            out.writeQuery(filter);
+        }
+
         public String key() {
             return key;
         }
@@ -92,19 +104,6 @@ public class FiltersAggregator extends BucketsAggregator {
             return builder;
         }
 
-        @Override
-        public KeyedFilter readFrom(StreamInput in) throws IOException {
-            String key = in.readString();
-            QueryBuilder<?> filter = in.readQuery();
-            return new KeyedFilter(key, filter);
-    }
-
-        @Override
-        public void writeTo(StreamOutput out) throws IOException {
-            out.writeString(key);
-            out.writeQuery(filter);
-        }
-
         @Override
         public int hashCode() {
             return Objects.hash(key, filter);

core/src/main/java/org/elasticsearch/search/aggregations/bucket/filters/FiltersAggregatorBuilder.java

@@ -100,7 +100,7 @@ public class FiltersAggregatorBuilder extends AggregatorBuilder<FiltersAggregato
         filters = new ArrayList<>(filtersSize);
         if (keyed) {
             for (int i = 0; i < filtersSize; i++) {
-                filters.add(KeyedFilter.PROTOTYPE.readFrom(in));
+                filters.add(new KeyedFilter(in));
             }
         } else {
             for (int i = 0; i < filtersSize; i++) {