From a4605645c44f1116978fbf74c3ac56945d2a0486 Mon Sep 17 00:00:00 2001
From: Armin Braun <me@obrown.io>
Date: Tue, 15 Dec 2020 13:39:17 +0100
Subject: [PATCH] Remove Lucene Precommit from PersistentCache (#66324)
 (#66331)

There is nothing gained from doing the precommit step explicitly here.
Also, we can just reuse the same map entries statically.
---
 .../cache/PersistentCache.java                  | 17 +++++++----------
 .../cache/PersistentCacheTests.java             |  7 ++-----
 2 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCache.java b/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCache.java
index affe69ac12663..bf9520623cb2e 100644
--- a/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCache.java
+++ b/x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCache.java
@@ -56,10 +56,12 @@
 import java.nio.file.SimpleFileVisitor;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -212,9 +214,6 @@ public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
     void commit() throws IOException {
         ensureOpen();
         try {
-            for (CacheIndexWriter writer : writers) {
-                writer.prepareCommit();
-            }
             for (CacheIndexWriter writer : writers) {
                 writer.commit();
             }
@@ -457,16 +456,14 @@ void deleteCacheFile(String cacheFileId) throws IOException {
             indexWriter.deleteDocuments(term);
         }
 
-        void prepareCommit() throws IOException {
-            logger.debug("preparing commit");
-            final Map<String, String> commitData = new HashMap<>(1);
-            commitData.put(NODE_VERSION_COMMIT_KEY, Integer.toString(Version.CURRENT.id));
-            indexWriter.setLiveCommitData(commitData.entrySet());
-            indexWriter.prepareCommit();
-        }
+        private static final Set<Map.Entry<String, String>> LUCENE_COMMIT_DATA = Collections.singletonMap(
+            NODE_VERSION_COMMIT_KEY,
+            Integer.toString(Version.CURRENT.id)
+        ).entrySet();
 
         void commit() throws IOException {
             logger.debug("committing");
+            indexWriter.setLiveCommitData(LUCENE_COMMIT_DATA);
             indexWriter.commit();
         }
 
diff --git a/x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCacheTests.java b/x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCacheTests.java
index 1c8a12685f6f6..454149ec3851c 100644
--- a/x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCacheTests.java
+++ b/x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/xpack/searchablesnapshots/cache/PersistentCacheTests.java
@@ -119,11 +119,8 @@ public void testCacheIndexWriter() throws Exception {
 
                 boolean commit = false;
                 if (frequently()) {
-                    writer.prepareCommit();
-                    if (frequently()) {
-                        writer.commit();
-                        commit = true;
-                    }
+                    writer.commit();
+                    commit = true;
                 }
 
                 if (commit) {