Core: Remove NestedDocsFilter, because it isn't used and also don't eagerly load it in bitset filter cache.

Closes #8414

src/main/java/org/elasticsearch/index/cache/bitset/BitsetFilterCache.java

@@ -45,7 +45,6 @@ import org.elasticsearch.index.mapper.DocumentMapper;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.internal.ParentFieldMapper;
 import org.elasticsearch.index.mapper.object.ObjectMapper;
-import org.elasticsearch.index.search.nested.NestedDocsFilter;
 import org.elasticsearch.index.search.nested.NonNestedDocsFilter;
 import org.elasticsearch.index.service.IndexService;
 import org.elasticsearch.index.service.InternalIndexService;
@@ -268,7 +267,6 @@ public class BitsetFilterCache extends AbstractIndexComponent implements LeafRea
 
             if (hasNested) {
                 warmUp.add(NonNestedDocsFilter.INSTANCE);
-                warmUp.add(NestedDocsFilter.INSTANCE);
             }
 
             final Executor executor = threadPool.executor(executor());

src/main/java/org/elasticsearch/index/search/nested/NestedDocsFilter.java

@@ -1,67 +0,0 @@
-/*
- * Licensed to Elasticsearch 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.index.search.nested;
-
-import org.apache.lucene.index.LeafReaderContext;
-import org.apache.lucene.index.Term;
-import org.apache.lucene.search.DocIdSet;
-import org.apache.lucene.search.Filter;
-import org.apache.lucene.search.PrefixFilter;
-import org.apache.lucene.util.Bits;
-import org.apache.lucene.util.BytesRef;
-import org.elasticsearch.index.mapper.internal.TypeFieldMapper;
-
-import java.io.IOException;
-
-/**
- * Filter that returns all nested documents.
- * A nested document is a sub documents that belong to a root document.
- * Nested documents share the unique id and type and optionally the _source with root documents.
- */
-public class NestedDocsFilter extends Filter {
-
-    public static final NestedDocsFilter INSTANCE = new NestedDocsFilter();
-
-    private final Filter filter = nestedFilter();
-    private final int hashCode = filter.hashCode();
-
-    private NestedDocsFilter() {
-    }
-
-    @Override
-    public DocIdSet getDocIdSet(LeafReaderContext context, Bits acceptDocs) throws IOException {
-        return filter.getDocIdSet(context, acceptDocs);
-    }
-
-    @Override
-    public int hashCode() {
-        return hashCode;
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        return obj == INSTANCE;
-    }
-
-    static Filter nestedFilter() {
-        return new PrefixFilter(new Term(TypeFieldMapper.NAME, new BytesRef("__")));
-    }
-
-}

src/main/java/org/elasticsearch/index/search/nested/NonNestedDocsFilter.java

@@ -20,22 +20,29 @@
 package org.elasticsearch.index.search.nested;
 
 import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.index.Term;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.Filter;
+import org.apache.lucene.search.PrefixFilter;
 import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.common.lucene.search.NotFilter;
+import org.elasticsearch.index.mapper.internal.TypeFieldMapper;
 
 import java.io.IOException;
 
 /**
  * A filter that returns all root (non nested) documents.
+ *
  * Root documents have an unique id, a type and optionally have a _source and other indexed and stored fields.
+ * A nested document is a sub documents that belong to a root document.
+ * Nested documents share the unique id and type and optionally the _source with root documents.
  */
 public class NonNestedDocsFilter extends Filter {
 
     public static final NonNestedDocsFilter INSTANCE = new NonNestedDocsFilter();
 
-    private final Filter filter = new NotFilter(NestedDocsFilter.nestedFilter());
+    private final Filter filter = new NotFilter(nestedFilter());
     private final int hashCode = filter.hashCode();
 
     private NonNestedDocsFilter() {
@@ -55,4 +62,11 @@ public class NonNestedDocsFilter extends Filter {
     public boolean equals(Object obj) {
         return obj == INSTANCE;
     }
+
+    /**
+     * @return a filter that returns all nested documents.
+     */
+    private static Filter nestedFilter() {
+        return new PrefixFilter(new Term(TypeFieldMapper.NAME, new BytesRef("__")));
+    }
 }