Implements specific SimpleIndexReader#query method

Instead of relying on the default wrapping found in AbstractIndexReader.
This removes unnecessary indirection in SimpleIndexReader.

community/kernel/src/main/java/org/neo4j/kernel/impl/api/schema/BridgingIndexProgressor.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2002-2018 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.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.api.schema;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+import org.neo4j.internal.kernel.api.IndexQuery;
+import org.neo4j.kernel.api.schema.index.IndexDescriptor;
+import org.neo4j.storageengine.api.schema.IndexProgressor;
+import org.neo4j.values.storable.Value;
+
+/**
+ * Combine multiple progressor to act like one single logical progressor seen from client's perspective.
+ */
+public class BridgingIndexProgressor implements IndexProgressor.NodeValueClient, IndexProgressor
+{
+    private final NodeValueClient client;
+    private final int[] keys;
+    // This is a thread-safe queue because it can be used in parallel scenarios.
+    // The overhead of a concurrent queue in this case is negligable since typically there will be two or a very few number
+    // of progressors and each progressor has many results each
+    private final Queue<IndexProgressor> progressors = new ConcurrentLinkedQueue<>();
+    private IndexProgressor current;
+
+    public BridgingIndexProgressor( NodeValueClient client, int[] keys )
+    {
+        this.client = client;
+        this.keys = keys;
+    }
+
+    @Override
+    public boolean next()
+    {
+        if ( current == null )
+        {
+            current = progressors.poll();
+        }
+        while ( current != null )
+        {
+            if ( current.next() )
+            {
+                return true;
+            }
+            else
+            {
+                current.close();
+                current = progressors.poll();
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public boolean needsValues()
+    {
+        return client.needsValues();
+    }
+
+    @Override
+    public void close()
+    {
+        progressors.forEach( IndexProgressor::close );
+    }
+
+    @Override
+    public void initialize( IndexDescriptor descriptor, IndexProgressor progressor, IndexQuery[] queries )
+    {
+        assertKeysAlign( descriptor.schema().getPropertyIds() );
+        progressors.add( progressor );
+    }
+
+    private void assertKeysAlign( int[] keys )
+    {
+        for ( int i = 0; i < this.keys.length; i++ )
+        {
+            if ( this.keys[i] != keys[i] )
+            {
+                throw new UnsupportedOperationException( "Can not chain multiple progressors with different key set." );
+            }
+        }
+    }
+
+    @Override
+    public boolean acceptNode( long reference, Value[] values )
+    {
+        return client.acceptNode( reference, values );
+    }
+}

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

@@ -19,9 +19,7 @@
  */
 package org.neo4j.kernel.impl.index.schema.fusion;
 
-import java.util.ArrayDeque;
 import java.util.Arrays;
-import java.util.Queue;
 
 import org.neo4j.collection.primitive.PrimitiveLongResourceCollections;
 import org.neo4j.collection.primitive.PrimitiveLongResourceIterator;
@@ -32,6 +30,7 @@
 import org.neo4j.internal.kernel.api.IndexQuery.NumberRangePredicate;
 import org.neo4j.kernel.api.exceptions.index.IndexNotApplicableKernelException;
 import org.neo4j.kernel.api.schema.index.IndexDescriptor;
+import org.neo4j.kernel.impl.api.schema.BridgingIndexProgressor;
 import org.neo4j.kernel.impl.index.schema.fusion.FusionSchemaIndexProvider.Selector;
 import org.neo4j.storageengine.api.schema.IndexProgressor;
 import org.neo4j.storageengine.api.schema.IndexReader;
@@ -172,80 +171,4 @@ public boolean hasFullNumberPrecision( IndexQuery... predicates )
         }
         return predicates[0] instanceof NumberRangePredicate && nativeReader.hasFullNumberPrecision( predicates );
     }
-
-    /**
-     * Combine multiple progressor to act like one single logical progressor seen from clients perspective.
-     */
-    private static class BridgingIndexProgressor implements IndexProgressor.NodeValueClient, IndexProgressor
-    {
-        private final NodeValueClient client;
-        private final int[] keys;
-        private final Queue<IndexProgressor> progressors;
-        private IndexProgressor current;
-
-        BridgingIndexProgressor( NodeValueClient client, int[] keys )
-        {
-            this.client = client;
-            this.keys = keys;
-            progressors = new ArrayDeque<>();
-        }
-
-        @Override
-        public boolean next()
-        {
-            if ( current == null )
-            {
-                current = progressors.poll();
-            }
-            while ( current != null )
-            {
-                if ( current.next() )
-                {
-                    return true;
-                }
-                else
-                {
-                    current.close();
-                    current = progressors.poll();
-                }
-            }
-            return false;
-        }
-
-        @Override
-        public boolean needsValues()
-        {
-            return client.needsValues();
-        }
-
-        @Override
-        public void close()
-        {
-            progressors.forEach( IndexProgressor::close );
-        }
-
-        @Override
-        public void initialize( IndexDescriptor descriptor, IndexProgressor progressor, IndexQuery[] queries )
-        {
-            assertKeysAlign( descriptor.schema().getPropertyIds() );
-            progressors.add( progressor );
-        }
-
-        private void assertKeysAlign( int[] keys )
-        {
-            for ( int i = 0; i < this.keys.length; i++ )
-            {
-                if ( this.keys[i] != keys[i] )
-                {
-                    throw new UnsupportedOperationException( "Can not chain multiple progressors with different key set." );
-                }
-            }
-        }
-
-        @Override
-        public boolean acceptNode( long reference, Value[] values )
-        {
-            return client.acceptNode( reference, values );
-        }
-    }
 }