Move method to Lucene

Author: albertzaharovits

server/src/main/java/org/elasticsearch/common/lucene/Lucene.java

@@ -87,9 +87,12 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 public class Lucene {
 
@@ -128,6 +131,14 @@ public static Iterable<String> files(SegmentInfos infos) throws IOException {
         return Iterables.flatten(list);
     }
 
+    /**
+     * Returns the additional files that the {@param current} index commit introduces compared to the {@param previous} one.
+     */
+    public static Set<String> additionalFileNames(IndexCommit previous, IndexCommit current) throws IOException {
+        final Set<String> previousFiles = previous != null ? new HashSet<>(previous.getFileNames()) : Set.of();
+        return current.getFileNames().stream().filter(f -> previousFiles.contains(f) == false).collect(Collectors.toUnmodifiableSet());
+    }
+
     /**
      * Returns the number of documents in the index referenced by this {@link SegmentInfos}
      */

server/src/main/java/org/elasticsearch/index/engine/CombinedDeletionPolicy.java

@@ -30,6 +30,7 @@
 import java.util.Set;
 import java.util.function.LongSupplier;
 
+import static org.elasticsearch.common.lucene.Lucene.additionalFileNames;
 import static org.elasticsearch.index.engine.ElasticsearchIndexDeletionPolicy.CommitsListener.listOfNewFileNames;
 
 /**
@@ -131,7 +132,7 @@ public void onCommit(List<? extends IndexCommit> commits) throws IOException {
         assert assertSafeCommitUnchanged(safeCommit);
         if (commitsListener != null) {
             if (newCommit != null) {
-                final Set<String> additionalFiles = listOfNewFileNames(previousLastCommit, newCommit);
+                final Set<String> additionalFiles = additionalFileNames(previousLastCommit, newCommit);
                 commitsListener.onNewAcquiredCommit(newCommit, additionalFiles);
             }
             if (deletedCommits != null) {

server/src/main/java/org/elasticsearch/index/engine/ElasticsearchIndexDeletionPolicy.java

@@ -48,10 +48,5 @@ public interface CommitsListener {
         void onNewAcquiredCommit(IndexCommit commit, Set<String> additionalFiles);
 
         void onDeletedCommit(IndexCommit commit);
-
-        static Set<String> listOfNewFileNames(IndexCommit previous, IndexCommit current) throws IOException {
-            final Set<String> previousFiles = previous != null ? new HashSet<>(previous.getFileNames()) : Set.of();
-            return current.getFileNames().stream().filter(f -> previousFiles.contains(f) == false).collect(Collectors.toUnmodifiableSet());
-        }
     }
 }