From 68d16c2a65b4acd0ce1ca543ae53a82e2516f1e5 Mon Sep 17 00:00:00 2001
From: Jim Ferenczi <jimczi@apache.org>
Date: Thu, 7 Dec 2017 14:08:46 +0100
Subject: [PATCH] LUCENE-8082: Fix NPE in TopFieldCollectors that don't track
 total hit count

---
 .../lucene/search/TopFieldCollector.java      | 12 ++++++---
 .../lucene/search/TestTopFieldCollector.java  | 25 +++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/lucene/core/src/java/org/apache/lucene/search/TopFieldCollector.java b/lucene/core/src/java/org/apache/lucene/search/TopFieldCollector.java
index c3597e9da1c..3d85277fcb0 100644
--- a/lucene/core/src/java/org/apache/lucene/search/TopFieldCollector.java
+++ b/lucene/core/src/java/org/apache/lucene/search/TopFieldCollector.java
@@ -121,9 +121,11 @@ public abstract class TopFieldCollector extends TopDocsCollector<Entry> {
 
       final LeafFieldComparator[] comparators = queue.getComparators(context);
       final int[] reverseMul = queue.getReverseMul();
+      final Sort indexSort = context.reader().getMetaData().getSort();
       final boolean canEarlyTerminate = trackTotalHits == false &&
           trackMaxScore == false &&
-          canEarlyTerminate(sort, context.reader().getMetaData().getSort());
+          indexSort != null &&
+          canEarlyTerminate(sort, indexSort);
       final int initialTotalHits = totalHits;
 
       return new MultiComparatorLeafCollector(comparators, reverseMul, mayNeedScoresTwice) {
@@ -212,7 +214,9 @@ public abstract class TopFieldCollector extends TopDocsCollector<Entry> {
       this.trackTotalHits = trackTotalHits;
 
       // Must set maxScore to NEG_INF, or otherwise Math.max always returns NaN.
-      maxScore = Float.NEGATIVE_INFINITY;
+      if (trackMaxScore) {
+        maxScore = Float.NEGATIVE_INFINITY;
+      }
 
       FieldComparator<?>[] comparators = queue.comparators;
       // Tell all comparators their top value:
@@ -227,9 +231,11 @@ public abstract class TopFieldCollector extends TopDocsCollector<Entry> {
     public LeafCollector getLeafCollector(LeafReaderContext context) throws IOException {
       docBase = context.docBase;
       final int afterDoc = after.doc - docBase;
+      final Sort indexSort = context.reader().getMetaData().getSort();
       final boolean canEarlyTerminate = trackTotalHits == false &&
           trackMaxScore == false &&
-          canEarlyTerminate(sort, context.reader().getMetaData().getSort());
+          indexSort != null &&
+          canEarlyTerminate(sort, indexSort);
       final int initialTotalHits = totalHits;
       return new MultiComparatorLeafCollector(queue.getComparators(context), queue.getReverseMul(), mayNeedScoresTwice) {
 
diff --git a/lucene/core/src/test/org/apache/lucene/search/TestTopFieldCollector.java b/lucene/core/src/test/org/apache/lucene/search/TestTopFieldCollector.java
index 0b7dc5b501c..d8363f7cfd8 100644
--- a/lucene/core/src/test/org/apache/lucene/search/TestTopFieldCollector.java
+++ b/lucene/core/src/test/org/apache/lucene/search/TestTopFieldCollector.java
@@ -102,6 +102,31 @@ public class TestTopFieldCollector extends LuceneTestCase {
       assertTrue(Float.isNaN(td.getMaxScore()));
     }
   }
+
+  public void testSortWithoutTotalHitTracking() throws Exception {
+    Sort sort = new Sort(SortField.FIELD_DOC);
+    for(int i = 0; i < 2; i++) {
+      Query q = new MatchAllDocsQuery();
+      // check that setting trackTotalHits to false does not throw an NPE because
+      // the index is not sorted
+      TopDocsCollector<Entry> tdc;
+      if (i % 2 == 0) {
+        tdc =  TopFieldCollector.create(sort, 10, true, false, false, false);
+      } else {
+        FieldDoc fieldDoc = new FieldDoc(1, Float.NaN, new Object[] { 1 });
+        tdc = TopFieldCollector.create(sort, 10, fieldDoc, true, false, false, false);
+      }
+
+      is.search(q, tdc);
+
+      TopDocs td = tdc.topDocs();
+      ScoreDoc[] sd = td.scoreDocs;
+      for(int j = 0; j < sd.length; j++) {
+        assertTrue(Float.isNaN(sd[j].score));
+      }
+      assertTrue(Float.isNaN(td.getMaxScore()));
+    }
+  }
   
   public void testSortWithScoreNoMaxScoreTracking() throws Exception {