Specific interface for populator part supplier

community/kernel/src/main/java/org/neo4j/kernel/impl/index/schema/NativeIndexPopulatorPartSupplier.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2002-2018 "Neo4j,"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.kernel.impl.index.schema;
+
+import java.io.File;
+
+@FunctionalInterface
+interface NativeIndexPopulatorPartSupplier<KEY extends NativeIndexKey<KEY>,VALUE extends NativeIndexValue>
+{
+    NativeIndexPopulator<KEY,VALUE> part( File partFileName );
+}

community/kernel/src/main/java/org/neo4j/kernel/impl/index/schema/ParallelNativeIndexPopulator.java

@@ -28,7 +28,6 @@
 import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedDeque;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.function.Function;
 
 import org.neo4j.cursor.RawCursor;
 import org.neo4j.index.internal.gbptree.Hit;
@@ -68,7 +67,7 @@ class ParallelNativeIndexPopulator<KEY extends NativeIndexKey<KEY>,VALUE extends
     // from being created beyond that point.
     private volatile boolean closed;
 
-    ParallelNativeIndexPopulator( File baseIndexFile, IndexLayout<KEY,VALUE> layout, Function<File,NativeIndexPopulator<KEY,VALUE>> populatorSupplier )
+    ParallelNativeIndexPopulator( File baseIndexFile, IndexLayout<KEY,VALUE> layout, NativeIndexPopulatorPartSupplier<KEY,VALUE> partSupplier )
     {
         this.layout = layout;
         this.threadLocalPopulators = new ThreadLocal<ThreadLocalPopulator>()
@@ -86,14 +85,14 @@ protected synchronized ThreadLocalPopulator initialValue()
                 }
 
                 File file = new File( baseIndexFile + "-part-" + partPopulators.size() );
-                NativeIndexPopulator<KEY,VALUE> populator = populatorSupplier.apply( file );
+                NativeIndexPopulator<KEY,VALUE> populator = partSupplier.part( file );
                 ThreadLocalPopulator tlPopulator = new ThreadLocalPopulator( populator );
                 partPopulators.add( tlPopulator );
                 populator.create();
                 return tlPopulator;
             }
         };
-        this.completePopulator = populatorSupplier.apply( baseIndexFile );
+        this.completePopulator = partSupplier.part( baseIndexFile );
     }
 
     @Override