Relationship delete over Kernel API

community/kernel-api/src/main/java/org/neo4j/internal/kernel/api/Write.java

@@ -55,7 +55,7 @@ public interface Write
      * Delete a relationship
      * @param relationship the internal id of the relationship to delete
      */
-    void relationshipDelete( long relationship );
+    boolean relationshipDelete( long relationship ) throws AutoIndexingKernelException;
 
     /**
      * Add a label to a node

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

@@ -62,4 +62,34 @@ public void shouldSeeSingleRelationshipInTransaction() throws Exception
             tx.success();
         }
     }
+
+    @Test
+    public void shouldNotSeeSingleRelationshipWhichWasDeletedInTransaction() throws Exception
+    {
+        int label;
+        long n1, n2, r;
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            n1 = tx.dataWrite().nodeCreate();
+            n2 = tx.dataWrite().nodeCreate();
+            label = tx.tokenWrite().relationshipTypeGetOrCreateForName( "R" );
+
+            long decoyNode = tx.dataWrite().nodeCreate();
+            tx.dataWrite().relationshipCreate( n2, label, decoyNode ); // to have >1 relationship in the db
+
+            r = tx.dataWrite().relationshipCreate( n1, label, n2 );
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            assertTrue( "should delete relationship", tx.dataWrite().relationshipDelete( r ) );
+            try ( RelationshipScanCursor relationship = cursors.allocateRelationshipScanCursor() )
+            {
+                tx.dataRead().singleRelationship( r, relationship );
+                assertFalse( "should not find relationship", relationship.next() );
+            }
+            tx.success();
+        }
+    }
 }

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

@@ -27,8 +27,8 @@
 import java.util.List;
 
 import org.neo4j.graphdb.Node;
-import org.neo4j.graphdb.NotFoundException;
 import org.neo4j.graphdb.Relationship;
+import org.neo4j.graphdb.RelationshipType;
 import org.neo4j.helpers.collection.Iterables;
 import org.neo4j.internal.kernel.api.exceptions.KernelException;
 
@@ -37,7 +37,6 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
 import static org.neo4j.graphdb.Label.label;
 import static org.neo4j.values.storable.Values.NO_VALUE;
 import static org.neo4j.values.storable.Values.intValue;
@@ -120,4 +119,75 @@ public void shouldRollbackRelationshipOnFailure() throws Exception
             assertEquals( 0, graphDb.getNodeById( n1 ).getDegree() );
         }
     }
+
+    @Test
+    public void shouldDeleteRelationship() throws Exception
+    {
+        long n1, r;
+        try ( org.neo4j.graphdb.Transaction tx = graphDb.beginTx() )
+        {
+            Node node1 = graphDb.createNode();
+            Node node2 = graphDb.createNode();
+
+            n1 = node1.getId();
+            r = node1.createRelationshipTo( node2, RelationshipType.withName( "R" ) ).getId();
+
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            assertTrue( "should delete relationship", tx.dataWrite().relationshipDelete( r ) );
+            tx.success();
+        }
+
+        try ( org.neo4j.graphdb.Transaction ignore = graphDb.beginTx() )
+        {
+            assertEquals( 0, graphDb.getNodeById( n1 ).getDegree() );
+        }
+    }
+
+    @Test
+    public void shouldNotDeleteRelationshipThatDoesNotExist() throws Exception
+    {
+        long relationship = 0;
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            assertFalse( tx.dataWrite().relationshipDelete( relationship ) );
+            tx.failure();
+        }
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            assertFalse( tx.dataWrite().relationshipDelete( relationship ) );
+            tx.success();
+        }
+        // should not crash
+    }
+
+    @Test
+    public void shouldDeleteRelationshipAddedInTransaction() throws Exception
+    {
+        long n1, n2;
+        try ( org.neo4j.graphdb.Transaction tx = graphDb.beginTx() )
+        {
+            n1 = graphDb.createNode().getId();
+            n2 = graphDb.createNode().getId();
+            tx.success();
+        }
+
+        try ( Transaction tx = session.beginTransaction() )
+        {
+            int label = session.token().relationshipTypeGetOrCreateForName( "R" );
+            long r = tx.dataWrite().relationshipCreate( n1, label, n2 );
+
+            assertTrue( tx.dataWrite().relationshipDelete( r ) );
+            tx.success();
+        }
+
+        try ( org.neo4j.graphdb.Transaction ignore = graphDb.beginTx() )
+        {
+            assertEquals( 0, graphDb.getNodeById( n1 ).getDegree() );
+        }
+    }
 }

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

@@ -83,6 +83,7 @@ public class Operations implements Write, ExplicitIndexWrite
     private org.neo4j.kernel.impl.newapi.NodeCursor nodeCursor;
     private final IndexTxStateUpdater updater;
     private PropertyCursor propertyCursor;
+    private RelationshipScanCursor relationshipCursor;
     private final Cursors cursors;
     private final NodeSchemaMatcher schemaMatcher;
 
@@ -110,6 +111,7 @@ public void initialize()
     {
         this.nodeCursor = cursors.allocateNodeCursor();
         this.propertyCursor = cursors.allocatePropertyCursor();
+        this.relationshipCursor = cursors.allocateRelationshipScanCursor();
     }
 
     @Override
@@ -166,10 +168,22 @@ public long relationshipCreate( long sourceNode, int relationshipLabel, long tar
     }
 
     @Override
-    public void relationshipDelete( long relationship )
+    public boolean relationshipDelete( long relationship ) throws AutoIndexingKernelException
     {
         ktx.assertOpen();
-        throw new UnsupportedOperationException();
+
+        allStoreHolder.singleRelationship( relationship, relationshipCursor ); // tx-state aware
+
+        if ( relationshipCursor.next() )
+        {
+            autoIndexing.relationships().entityRemoved( this, relationship );
+            ktx.txState().relationshipDoDelete( relationship, relationshipCursor.getType(),
+                    relationshipCursor.sourceNodeReference(), relationshipCursor.targetNodeReference() );
+            return true;
+        }
+
+        // tried to delete relationship that does not exist
+        return false;
     }
 
     @Override