From 35ede0951150f272413e36d7fdf66503727e149d Mon Sep 17 00:00:00 2001
From: Martijn van Groningen <martijn.v.groningen@gmail.com>
Date: Sun, 26 Oct 2014 20:42:52 +0100
Subject: [PATCH] Core: Cleanup non nested filter to not flip the bits in the
 FixedBitSet returned by the wrapped filter.

If the filter producing the FBS were to be cached then it would flip bits each time the NonNestedDocsFilter was executed.
In our case we cache the NonNestedDocsFilter itself so that didn't happen each time this filter was used.
However the hashcode of NonNestedDocsFilter and NestedDocsFilter was the same, since NonNestedDocsFilter directly used NestedDocsFilter#hashCode()

Closes #8227
Closes #8232
---
 .../index/search/nested/NestedDocsFilter.java | 14 ++++++++---
 .../search/nested/NonNestedDocsFilter.java    | 24 ++++++-------------
 2 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/src/main/java/org/elasticsearch/index/search/nested/NestedDocsFilter.java b/src/main/java/org/elasticsearch/index/search/nested/NestedDocsFilter.java
index 0b46f6426cb..d9d31fb0303 100644
--- a/src/main/java/org/elasticsearch/index/search/nested/NestedDocsFilter.java
+++ b/src/main/java/org/elasticsearch/index/search/nested/NestedDocsFilter.java
@@ -30,16 +30,19 @@ 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 PrefixFilter filter = new PrefixFilter(new Term(TypeFieldMapper.NAME, new BytesRef("__")));
-
+    private final Filter filter = nestedFilter();
     private final int hashCode = filter.hashCode();
 
     private NestedDocsFilter() {
-
     }
 
     @Override
@@ -56,4 +59,9 @@ public class NestedDocsFilter extends Filter {
     public boolean equals(Object obj) {
         return obj == INSTANCE;
     }
+
+    static Filter nestedFilter() {
+        return new PrefixFilter(new Term(TypeFieldMapper.NAME, new BytesRef("__")));
+    }
+
 }
\ No newline at end of file
diff --git a/src/main/java/org/elasticsearch/index/search/nested/NonNestedDocsFilter.java b/src/main/java/org/elasticsearch/index/search/nested/NonNestedDocsFilter.java
index 50e1df9e731..6de5f27910e 100644
--- a/src/main/java/org/elasticsearch/index/search/nested/NonNestedDocsFilter.java
+++ b/src/main/java/org/elasticsearch/index/search/nested/NonNestedDocsFilter.java
@@ -20,40 +20,30 @@
 package org.elasticsearch.index.search.nested;
 
 import org.apache.lucene.index.AtomicReaderContext;
-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.apache.lucene.util.FixedBitSet;
-import org.elasticsearch.common.lucene.docset.DocIdSets;
-import org.elasticsearch.index.mapper.internal.TypeFieldMapper;
+import org.elasticsearch.common.lucene.search.NotFilter;
 
 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.
+ */
 public class NonNestedDocsFilter extends Filter {
 
     public static final NonNestedDocsFilter INSTANCE = new NonNestedDocsFilter();
 
-    private final PrefixFilter filter = new PrefixFilter(new Term(TypeFieldMapper.NAME, new BytesRef("__")));
-
+    private final Filter filter = new NotFilter(NestedDocsFilter.nestedFilter());
     private final int hashCode = filter.hashCode();
 
     private NonNestedDocsFilter() {
-
     }
 
     @Override
     public DocIdSet getDocIdSet(AtomicReaderContext context, Bits acceptDocs) throws IOException {
-        DocIdSet docSet = filter.getDocIdSet(context, acceptDocs);
-        if (DocIdSets.isEmpty(docSet)) {
-            // will almost never happen, and we need an OpenBitSet for the parent filter in
-            // BlockJoinQuery, we cache it anyhow...
-            docSet = new FixedBitSet(context.reader().maxDoc());
-        }
-        ((FixedBitSet) docSet).flip(0, context.reader().maxDoc());
-        return docSet;
+        return filter.getDocIdSet(context, acceptDocs);
     }
 
     @Override