TxState aware relationship traversal of non-dense node

community/kernel-api/src/test/java/org/neo4j/internal/kernel/api/RelationshipTransactionStateTestBase.java

@@ -93,4 +93,98 @@ public void shouldNotSeeSingleRelationshipWhichWasDeletedInTransaction() throws
             tx.success();
         }
     }
+
+    @Test
+    public void shouldSeeRelationshipInTransaction() throws Exception
+    {
+        long n1, n2;
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            n1 = tx.dataWrite().nodeCreate();
+            n2 = tx.dataWrite().nodeCreate();
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            int label = tx.tokenWrite().relationshipTypeGetOrCreateForName( "R" );
+            long r = tx.dataWrite().relationshipCreate( n1, label, n2 );
+            try ( NodeCursor node = cursors.allocateNodeCursor();
+                  RelationshipTraversalCursor relationship = cursors.allocateRelationshipTraversalCursor() )
+            {
+                tx.dataRead().singleNode( n1, node );
+                assertTrue( "should access node", node.next() );
+
+                node.allRelationships( relationship );
+                assertTrue( "should find relationship", relationship.next() );
+                assertEquals( r, relationship.relationshipReference() );
+
+                assertFalse( "should only find one relationship", relationship.next() );
+            }
+            tx.success();
+        }
+    }
+
+    @Test
+    public void shouldNotSeeRelationshipDeletedInTransaction() throws Exception
+    {
+        long n1, n2, r;
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            n1 = tx.dataWrite().nodeCreate();
+            n2 = tx.dataWrite().nodeCreate();
+
+            int label = tx.tokenWrite().relationshipTypeGetOrCreateForName( "R" );
+            r = tx.dataWrite().relationshipCreate( n1, label, n2 );
+
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            tx.dataWrite().relationshipDelete( r );
+            try ( NodeCursor node = cursors.allocateNodeCursor();
+                  RelationshipTraversalCursor relationship = cursors.allocateRelationshipTraversalCursor() )
+            {
+                tx.dataRead().singleNode( n1, node );
+                assertTrue( "should access node", node.next() );
+
+                node.allRelationships( relationship );
+                assertFalse( "should not find relationship", relationship.next() );
+            }
+            tx.success();
+        }
+    }
+
+    @Test
+    public void shouldSeeRelationshipInTransactionBeforeCursorInitialization() throws Exception
+    {
+        long n1, n2;
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            n1 = tx.dataWrite().nodeCreate();
+            n2 = tx.dataWrite().nodeCreate();
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            int label = tx.tokenWrite().relationshipTypeGetOrCreateForName( "R" );
+            long r = tx.dataWrite().relationshipCreate( n1, label, n2 );
+            try ( NodeCursor node = cursors.allocateNodeCursor();
+                    RelationshipTraversalCursor relationship = cursors.allocateRelationshipTraversalCursor() )
+            {
+                tx.dataRead().singleNode( n1, node );
+                assertTrue( "should access node", node.next() );
+
+                node.allRelationships( relationship );
+                assertTrue( "should find relationship", relationship.next() );
+                assertEquals( r, relationship.relationshipReference() );
+
+                tx.dataWrite().relationshipCreate( n1, label, n2 ); // should not be seen
+                assertFalse( "should not find relationship added after cursor init", relationship.next() );
+            }
+            tx.success();
+        }
+    }
 }

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

@@ -697,7 +697,7 @@ public Cursor<RelationshipItem> augmentNodeRelationshipCursor( Cursor<Relationsh
             NodeState nodeState,
             Direction direction )
     {
-        return nodeState.hasPropertyChanges() || nodeState.hasRelationshipChanges()
+        return nodeState.hasRelationshipChanges()
                ? iteratorRelationshipCursor.get().init( cursor, nodeState.getAddedRelationships( direction ) )
                : cursor;
     }
@@ -707,7 +707,7 @@ public Cursor<RelationshipItem> augmentNodeRelationshipCursor( Cursor<Relationsh
             Direction direction,
             int[] relTypes )
     {
-        return nodeState.hasPropertyChanges() || nodeState.hasRelationshipChanges()
+        return nodeState.hasRelationshipChanges()
                ? iteratorRelationshipCursor.get().init( cursor, nodeState.getAddedRelationships( direction, relTypes ) )
                : cursor;
     }

community/kernel/src/main/java/org/neo4j/kernel/impl/newapi/NodeCursor.java

@@ -176,10 +176,11 @@ public boolean next()
             reset();
             return false;
         }
+
         // Check tx state
         boolean hasChanges = hasChanges();
-
         TransactionState txs = hasChanges ? read.txState() : null;
+
         do
         {
             if ( hasChanges && containsNode( txs ) )

community/kernel/src/main/java/org/neo4j/kernel/impl/newapi/Read.java

@@ -252,7 +252,7 @@ else if ( hasDirectFlag( reference ) ) // the relationships for this node are no
     public final void relationships(
             long nodeReference, long reference, org.neo4j.internal.kernel.api.RelationshipTraversalCursor cursor )
     {
-        /* TODO: There are actually five (5!) different ways a relationship traversal cursor can be initialized:
+        /* There are 5 different ways a relationship traversal cursor can be initialized:
          *
          * 1. From a batched group in a detached way. This happens when the user manually retrieves the relationships
          *    references from the group cursor and passes it to this method and if the group cursor was based on having
@@ -282,7 +282,8 @@ public final void relationships(
         ktx.assertOpen();
         if ( reference == NO_ID ) // there are no relationships for this node
         {
-            cursor.close();
+            // still initiate cursor in case there are tx-state additions
+            ((RelationshipTraversalCursor) cursor).chain( nodeReference, reference, this );
         }
         else if ( hasGroupFlag( reference ) ) // this reference is actually to a group record
         {

community/kernel/src/main/java/org/neo4j/kernel/impl/newapi/RelationshipCursor.java

@@ -19,19 +19,14 @@
  */
 package org.neo4j.kernel.impl.newapi;
 
-import java.util.Set;
-
 import org.neo4j.internal.kernel.api.RelationshipDataAccessor;
 import org.neo4j.kernel.impl.api.RelationshipVisitor;
 import org.neo4j.kernel.impl.store.record.RelationshipRecord;
 
-import static java.util.Collections.emptySet;
-
 abstract class RelationshipCursor extends RelationshipRecord implements RelationshipDataAccessor, RelationshipVisitor<RuntimeException>
 {
     Read read;
     private HasChanges hasChanges = HasChanges.MAYBE;
-    Set<Long> addedRelationships;
 
     RelationshipCursor()
     {
@@ -42,7 +37,6 @@ protected void init( Read read )
     {
         this.read = read;
         this.hasChanges = HasChanges.MAYBE;
-        this.addedRelationships = emptySet();
     }
 
     @Override
@@ -99,7 +93,7 @@ public long propertiesReference()
         return getNextProp();
     }
 
-    protected abstract boolean shouldGetAddedTxStateSnapshot();
+    protected abstract void collectAddedTxStateSnapshot();
 
     /**
      * RelationshipCursor should only see changes that are there from the beginning
@@ -113,10 +107,7 @@ protected boolean hasChanges()
             boolean changes = read.hasTxStateWithChanges();
             if ( changes )
             {
-                if ( shouldGetAddedTxStateSnapshot() )
-                {
-                    addedRelationships = read.txState().addedAndRemovedRelationships().getAddedSnapshot();
-                }
+                collectAddedTxStateSnapshot();
                 hasChanges = HasChanges.YES;
             }
             else

community/kernel/src/main/java/org/neo4j/kernel/impl/newapi/RelationshipScanCursor.java

@@ -19,15 +19,20 @@
  */
 package org.neo4j.kernel.impl.newapi;
 
+import java.util.Set;
+
 import org.neo4j.io.pagecache.PageCursor;
 import org.neo4j.kernel.api.txstate.TransactionState;
 
+import static java.util.Collections.emptySet;
+
 class RelationshipScanCursor extends RelationshipCursor implements org.neo4j.internal.kernel.api.RelationshipScanCursor
 {
     private int label;
     private long next;
     private long highMark;
     private PageCursor pageCursor;
+    Set<Long> addedRelationships;
 
     void scan( int label, Read read )
     {
@@ -43,6 +48,7 @@ void scan( int label, Read read )
         this.label = label;
         highMark = read.relationshipHighMark();
         init( read );
+        this.addedRelationships = emptySet();
     }
 
     void single( long reference, Read read )
@@ -59,6 +65,7 @@ void single( long reference, Read read )
         label = -1;
         highMark = NO_ID;
         init( read );
+        this.addedRelationships = emptySet();
     }
 
     @Override
@@ -172,8 +179,11 @@ private boolean isSingle()
         return highMark == NO_ID;
     }
 
-    protected boolean shouldGetAddedTxStateSnapshot()
+    protected void collectAddedTxStateSnapshot()
     {
-        return !isSingle();
+        if ( !isSingle() )
+        {
+            addedRelationships = read.txState().addedAndRemovedRelationships().getAddedSnapshot();
+        }
     }
 }