Manage resource iterators explicitly

Knowledge about iterators' inherent resources must be reflected in
API contracts, not hidden under the hood as implicit "instanceof" check.

community/kernel/src/main/java/org/neo4j/kernel/impl/api/StateHandlingStatementOperations.java

@@ -829,19 +829,20 @@ public long nodeGetFromUniqueIndexSeek(
             KernelStatement state, SchemaIndexDescriptor index, IndexQuery.ExactPredicate... query )
             throws IndexNotFoundKernelException, IndexNotApplicableKernelException
     {
-        IndexReader reader = state.getStoreStatement().getFreshIndexReader( index );
-
-        /* Here we have an intricate scenario where we need to return the PrimitiveLongIterator
-         * since subsequent filtering will happen outside, but at the same time have the ability to
-         * close the IndexReader when done iterating over the lookup result. This is because we get
-         * a fresh reader that isn't associated with the current transaction and hence will not be
-         * automatically closed. */
-        PrimitiveLongResourceIterator committed = resourceIterator( reader.query( query ), reader );
-        PrimitiveLongResourceIterator exactMatches = reader.hasFullValuePrecision( query )
-                ? committed : LookupFilter.exactIndexMatches( this, state, committed, query );
-        PrimitiveLongIterator changesFiltered =
-                filterIndexStateChangesForSeek( state, exactMatches, index, IndexQuery.asValueTuple( query ) );
-        return single( resourceIterator( changesFiltered, committed ), NO_SUCH_NODE );
+        try ( IndexReader reader = state.getStoreStatement().getFreshIndexReader( index ) )
+        {
+            /* Here we have an intricate scenario where we need to return the PrimitiveLongIterator
+             * since subsequent filtering will happen outside, but at the same time have the ability to
+             * close the IndexReader when done iterating over the lookup result. This is because we get
+             * a fresh reader that isn't associated with the current transaction and hence will not be
+             * automatically closed. */
+            PrimitiveLongResourceIterator committed = reader.query( query );
+            PrimitiveLongResourceIterator exactMatches = reader.hasFullValuePrecision( query )
+                                                         ? committed : LookupFilter.exactIndexMatches( this, state, committed, query );
+            PrimitiveLongResourceIterator changesFiltered =
+                    filterIndexStateChangesForSeek( state, exactMatches, index, IndexQuery.asValueTuple( query ) );
+            return single( resourceIterator( changesFiltered, committed ), NO_SUCH_NODE );
+        }
     }
 
     @Override

community/kernel/src/main/java/org/neo4j/kernel/impl/api/state/TxState.java

@@ -33,7 +33,6 @@
 import org.neo4j.collection.primitive.PrimitiveIntSet;
 import org.neo4j.collection.primitive.PrimitiveLongIterator;
 import org.neo4j.collection.primitive.PrimitiveLongObjectMap;
-import org.neo4j.collection.primitive.PrimitiveLongResourceIterator;
 import org.neo4j.collection.primitive.PrimitiveLongSet;
 import org.neo4j.cursor.Cursor;
 import org.neo4j.helpers.collection.Iterables;
@@ -1264,7 +1263,7 @@ private PropertyChanges nodePropertyChanges()
     }
 
     @Override
-    public PrimitiveLongResourceIterator augmentNodesGetAll( PrimitiveLongIterator committed )
+    public PrimitiveLongIterator augmentNodesGetAll( PrimitiveLongIterator committed )
     {
         return addedAndRemovedNodes().augment( committed );
     }

community/kernel/src/main/java/org/neo4j/kernel/impl/util/diffsets/DiffApplyingLongIterator.java

@@ -21,6 +21,7 @@
 
 import java.util.Iterator;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 import org.neo4j.collection.primitive.PrimitiveLongCollections.PrimitiveLongBaseIterator;
 import org.neo4j.collection.primitive.PrimitiveLongIterator;
@@ -32,7 +33,7 @@
  * If the given source is a Resource, then so is this DiffApplyingPrimitiveLongIterator.
  */
 
-public class DiffApplyingLongIterator extends PrimitiveLongBaseIterator implements PrimitiveLongResourceIterator
+class DiffApplyingLongIterator extends PrimitiveLongBaseIterator implements PrimitiveLongResourceIterator
 {
     protected enum Phase
     {
@@ -70,15 +71,28 @@ boolean fetchNext( DiffApplyingLongIterator self )
     private final Iterator<?> addedElementsIterator;
     private final Set<?> addedElements;
     private final Set<?> removedElements;
+    @Nullable
+    private final Resource resource;
     protected Phase phase;
 
-    DiffApplyingLongIterator( PrimitiveLongIterator source, Set<?> addedElements, Set<?> removedElements )
+    DiffApplyingLongIterator( PrimitiveLongIterator source, Set<?> addedElements, Set<?> removedElements, @Nullable Resource resource )
     {
         this.source = source;
         this.addedElements = addedElements;
         this.addedElementsIterator = addedElements.iterator();
         this.removedElements = removedElements;
-        phase = Phase.FILTERED_SOURCE;
+        this.resource = resource;
+        this.phase = Phase.FILTERED_SOURCE;
+    }
+
+    static PrimitiveLongIterator augment( PrimitiveLongIterator source, Set<?> addedElements, Set<?> removedElements )
+    {
+        return new DiffApplyingLongIterator( source, addedElements, removedElements, null );
+    }
+
+    static PrimitiveLongResourceIterator augment( PrimitiveLongResourceIterator source, Set<?> addedElements, Set<?> removedElements )
+    {
+        return new DiffApplyingLongIterator( source, addedElements, removedElements, source );
     }
 
     @Override
@@ -103,20 +117,20 @@ private boolean computeNextFromSourceAndFilter()
 
     private void transitionToAddedElements()
     {
-        phase = !addedElementsIterator.hasNext() ? Phase.NO_ADDED_ELEMENTS : Phase.ADDED_ELEMENTS;
+        phase = addedElementsIterator.hasNext() ? Phase.ADDED_ELEMENTS : Phase.NO_ADDED_ELEMENTS;
     }
 
     private boolean computeNextFromAddedElements()
     {
-        return addedElementsIterator.hasNext() && next((Long) addedElementsIterator.next());
+        return addedElementsIterator.hasNext() && next( (Long) addedElementsIterator.next() );
     }
 
     @Override
     public void close()
     {
-        if ( source instanceof Resource )
+        if ( resource != null )
         {
-            ((Resource) source).close();
+            resource.close();
         }
     }
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/util/diffsets/DiffApplyingPrimitiveLongIterator.java

@@ -19,16 +19,18 @@
  */
 package org.neo4j.kernel.impl.util.diffsets;
 
+import javax.annotation.Nullable;
+
 import org.neo4j.collection.primitive.PrimitiveLongCollections.PrimitiveLongBaseIterator;
 import org.neo4j.collection.primitive.PrimitiveLongIterator;
+import org.neo4j.collection.primitive.PrimitiveLongResourceIterator;
 import org.neo4j.collection.primitive.PrimitiveLongSet;
 import org.neo4j.graphdb.Resource;
 
 /**
  * Applies a diffset to the provided {@link PrimitiveLongIterator}.
- * If the given source is a {@link Resource}, it will be closed on {@link #close()}.
  */
-public class DiffApplyingPrimitiveLongIterator extends PrimitiveLongBaseIterator implements Resource
+class DiffApplyingPrimitiveLongIterator extends PrimitiveLongBaseIterator implements PrimitiveLongResourceIterator
 {
     protected enum Phase
     {
@@ -66,16 +68,29 @@ boolean fetchNext( DiffApplyingPrimitiveLongIterator self )
     private final PrimitiveLongIterator addedElementsIterator;
     private final PrimitiveLongSet addedElements;
     private final PrimitiveLongSet removedElements;
-    protected Phase phase;
+    @Nullable
+    private final Resource resource;
+    private Phase phase;
 
-    DiffApplyingPrimitiveLongIterator( PrimitiveLongIterator source, PrimitiveLongSet addedElements,
-            PrimitiveLongSet removedElements )
+    private DiffApplyingPrimitiveLongIterator( PrimitiveLongIterator source, PrimitiveLongSet addedElements, PrimitiveLongSet removedElements,
+            @Nullable Resource resource )
     {
         this.source = source;
         this.addedElements = addedElements;
         this.addedElementsIterator = addedElements.iterator();
         this.removedElements = removedElements;
-        phase = Phase.FILTERED_SOURCE;
+        this.resource = resource;
+        this.phase = Phase.FILTERED_SOURCE;
+    }
+
+    static PrimitiveLongIterator augment( PrimitiveLongIterator source, PrimitiveLongSet addedElements, PrimitiveLongSet removedElements )
+    {
+        return new DiffApplyingPrimitiveLongIterator( source, addedElements, removedElements, null );
+    }
+
+    static PrimitiveLongResourceIterator augment( PrimitiveLongResourceIterator source, PrimitiveLongSet addedElements, PrimitiveLongSet removedElements )
+    {
+        return new DiffApplyingPrimitiveLongIterator( source, addedElements, removedElements, source );
     }
 
     @Override
@@ -100,7 +115,7 @@ private boolean computeNextFromSourceAndFilter()
 
     private void transitionToAddedElements()
     {
-        phase = !addedElementsIterator.hasNext() ? Phase.NO_ADDED_ELEMENTS : Phase.ADDED_ELEMENTS;
+        phase = addedElementsIterator.hasNext() ? Phase.ADDED_ELEMENTS : Phase.NO_ADDED_ELEMENTS;
     }
 
     private boolean computeNextFromAddedElements()
@@ -111,9 +126,9 @@ private boolean computeNextFromAddedElements()
     @Override
     public void close()
     {
-        if ( source instanceof Resource )
+        if ( resource != null )
         {
-            ((Resource) source).close();
+            resource.close();
         }
     }
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/util/diffsets/DiffApplyingRelationshipIterator.java

@@ -29,16 +29,14 @@
  * Applies a diffset to the given source {@link RelationshipIterator}.
  * If the given source is a {@link Resource}, then so is this {@link DiffApplyingRelationshipIterator}.
  */
-public class DiffApplyingRelationshipIterator extends DiffApplyingLongIterator implements RelationshipIterator
+class DiffApplyingRelationshipIterator extends DiffApplyingLongIterator implements RelationshipIterator
 {
     private final RelationshipVisitor.Home sourceHome;
     private final RelationshipVisitor.Home addedHome;
 
-    public DiffApplyingRelationshipIterator( RelationshipIterator source,
-                                             Set<?> addedElements, Set<?> removedElements,
-                                             RelationshipVisitor.Home addedHome )
+    DiffApplyingRelationshipIterator( RelationshipIterator source, Set<?> addedElements, Set<?> removedElements, RelationshipVisitor.Home addedHome )
     {
-        super( source, addedElements, removedElements );
+        super( source, addedElements, removedElements, null );
         this.sourceHome = source;
         this.addedHome = addedHome;
     }

community/kernel/src/main/java/org/neo4j/kernel/impl/util/diffsets/DiffSets.java

@@ -23,7 +23,6 @@
 import java.util.Set;
 import java.util.function.Predicate;
 
-import org.neo4j.collection.primitive.PrimitiveIntIterator;
 import org.neo4j.collection.primitive.PrimitiveLongIterator;
 import org.neo4j.collection.primitive.PrimitiveLongResourceIterator;
 import org.neo4j.helpers.collection.Iterables;
@@ -37,7 +36,7 @@
  *
  * @param <T> type of elements
  */
-public class DiffSets<T> extends SuperDiffSets<T,PrimitiveLongResourceIterator, PrimitiveLongIterator> implements ReadableDiffSets<T>
+public class DiffSets<T> extends SuperDiffSets<T> implements ReadableDiffSets<T>
 {
     public DiffSets()
     {
@@ -50,21 +49,21 @@ public DiffSets( Set<T> addedElements, Set<T> removedElements )
     }
 
     @Override
-    public PrimitiveLongResourceIterator augment( final PrimitiveLongIterator source )
+    public PrimitiveLongIterator augment( final PrimitiveLongIterator source )
     {
-        return new DiffApplyingLongIterator( source, added( false ), removed( false ) );
+        return DiffApplyingLongIterator.augment( source, added( false ), removed( false ) );
     }
 
     @Override
-    public PrimitiveIntIterator augment( final PrimitiveIntIterator source )
+    public PrimitiveLongResourceIterator augment( PrimitiveLongResourceIterator source )
     {
-        return new DiffApplyingIntIterator( source, added( false ), removed( false ) );
+        return DiffApplyingLongIterator.augment( source, added( false ), removed( false ) );
     }
 
     @Override
-    public PrimitiveLongResourceIterator augmentWithRemovals( final PrimitiveLongIterator source )
+    public PrimitiveLongResourceIterator augmentWithRemovals( PrimitiveLongResourceIterator source )
     {
-        return new DiffApplyingLongIterator( source, Collections.emptySet(), removed( false ) );
+        return DiffApplyingLongIterator.augment( source, Collections.emptySet(), removed( false ) );
     }
 
     @Override