From d22dd437f18d454128988666e4baf75692fa0b5e Mon Sep 17 00:00:00 2001
From: Armin Braun <me@obrown.io>
Date: Fri, 3 Jul 2020 09:18:14 +0200
Subject: [PATCH] Fix Two Common Zero Len Array Instantiations (#58944)
 (#58993)

Two spots I found in which we commonly instatiate a non-trivial number of zero length arrays.
---
 .../replication/ReplicationResponse.java        | 17 ++++++++---------
 .../org/elasticsearch/common/lucene/Lucene.java | 12 +++++++++---
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/action/support/replication/ReplicationResponse.java b/server/src/main/java/org/elasticsearch/action/support/replication/ReplicationResponse.java
index 73cda9298c8..70da7a6847c 100644
--- a/server/src/main/java/org/elasticsearch/action/support/replication/ReplicationResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/support/replication/ReplicationResponse.java
@@ -87,9 +87,11 @@ public class ReplicationResponse extends ActionResponse {
             total = in.readVInt();
             successful = in.readVInt();
             int size = in.readVInt();
-            failures = new Failure[size];
-            for (int i = 0; i < size; i++) {
-                failures[i] = new Failure(in);
+            if (size > 0) {
+                failures = new Failure[size];
+                for (int i = 0; i < size; i++) {
+                    failures[i] = new Failure(in);
+                }
             }
         }
 
@@ -223,9 +225,9 @@ public class ReplicationResponse extends ActionResponse {
             private static final String STATUS = "status";
             private static final String PRIMARY = "primary";
 
-            private ShardId shardId;
-            private String nodeId;
-            private boolean primary;
+            private final ShardId shardId;
+            private final String nodeId;
+            private final boolean primary;
 
             public Failure(StreamInput in) throws IOException {
                 shardId = new ShardId(in);
@@ -244,9 +246,6 @@ public class ReplicationResponse extends ActionResponse {
                 this.primary = primary;
             }
 
-            Failure() {
-            }
-
             public ShardId fullShardId() {
                 return shardId;
             }
diff --git a/server/src/main/java/org/elasticsearch/common/lucene/Lucene.java b/server/src/main/java/org/elasticsearch/common/lucene/Lucene.java
index 44d6b3a87dd..40e43c5c660 100644
--- a/server/src/main/java/org/elasticsearch/common/lucene/Lucene.java
+++ b/server/src/main/java/org/elasticsearch/common/lucene/Lucene.java
@@ -306,9 +306,15 @@ public class Lucene {
             TotalHits totalHits = readTotalHits(in);
             float maxScore = in.readFloat();
 
-            ScoreDoc[] scoreDocs = new ScoreDoc[in.readVInt()];
-            for (int i = 0; i < scoreDocs.length; i++) {
-                scoreDocs[i] = new ScoreDoc(in.readVInt(), in.readFloat());
+            final int scoreDocCount = in.readVInt();
+            final ScoreDoc[] scoreDocs;
+            if (scoreDocCount == 0) {
+                scoreDocs = EMPTY_SCORE_DOCS;
+            } else {
+                scoreDocs = new ScoreDoc[scoreDocCount];
+                for (int i = 0; i < scoreDocs.length; i++) {
+                    scoreDocs[i] = new ScoreDoc(in.readVInt(), in.readFloat());
+                }
             }
             return new TopDocsAndMaxScore(new TopDocs(totalHits, scoreDocs), maxScore);
         } else if (type == 1) {