Fixes from code review

- set read to null on close in cursors
- some style
- some documentation

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

@@ -62,6 +62,8 @@ enum Type
 
     /**
      * @return The Write operations of the graph.
+     * @throws InvalidTransactionTypeKernelException when transaction cannot be upgraded to a write transaction. This
+     * can happen when there have been schema modifications.
      */
     Write dataWrite() throws InvalidTransactionTypeKernelException;
 

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

@@ -84,7 +84,7 @@ public Value propertyValue()
     @Override
     public <E extends Exception> void writeTo( ValueWriter<E> target )
     {
-
+        throw new UnsupportedOperationException( "not implemented" );
     }
 
     @Override

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

@@ -199,7 +199,7 @@ public KernelTransactionImplementation( StatementOperationParts statementOperati
         this.userMetaData = new HashMap<>();
         AllStoreHolder allStoreHolder =
                 new AllStoreHolder( storageEngine, storageStatement, this, cursors, explicitIndexStore,
-                        this::assertTransactionOpen );
+                        this::assertOpen );
         this.operations =
                 new Operations(
                         allStoreHolder,
@@ -462,6 +462,15 @@ private void assertTransactionOpen()
         }
     }
 
+    private void assertOpen()
+    {
+        Optional<Status> terminationReason = getReasonIfTerminated();
+        if ( terminationReason.isPresent() )
+        {
+            throw new TransactionTerminatedException( terminationReason.get() );
+        }
+    }
+
     private boolean hasChanges()
     {
         return hasTxStateWithChanges() || hasExplicitIndexChanges();

community/kernel/src/main/java/org/neo4j/kernel/impl/core/NodeProxy.java

@@ -449,9 +449,9 @@ public Map<String,Object> getAllProperties()
         CursorFactory cursors = transaction.cursors();
         Map<String,Object> properties = new HashMap<>();
 
-        try ( NodeCursor nodes = cursors.allocateNodeCursor();
-              PropertyCursor propertyCursor = cursors.allocatePropertyCursor();
-              Statement ignore = actions.statement() )
+        try ( Statement ignore = actions.statement();
+              NodeCursor nodes = cursors.allocateNodeCursor();
+              PropertyCursor propertyCursor = cursors.allocatePropertyCursor() )
         {
             Token token = transaction.token();
             transaction.dataRead().singleNode( nodeId, nodes );

community/kernel/src/main/java/org/neo4j/kernel/impl/factory/GraphDatabaseFacade.java

@@ -332,8 +332,9 @@ public Node getNodeById( long id )
         }
 
         KernelTransaction ktx = spi.currentTransaction();
-        try ( NodeCursor nodeCursor = ktx.cursors().allocateNodeCursor();
-              Statement ignore = spi.currentStatement() )
+        try ( Statement ignore = spi.currentStatement();
+              NodeCursor nodeCursor = ktx.cursors().allocateNodeCursor()
+        )
         {
             ktx.dataRead().singleNode( id, nodeCursor );
             if ( !nodeCursor.next() )

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

@@ -302,7 +302,7 @@ ArrayValue array( PropertyCursor cursor, long reference, PageCursor page )
         return PropertyUtil.readArrayFromBuffer( buffer );
     }
 
-    public boolean nodeExists( long id )
+    public boolean nodeExistsInStore( long id )
     {
         return storeReadLayer.nodeExists( id );
     }

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

@@ -19,13 +19,10 @@
  */
 package org.neo4j.kernel.impl.newapi;
 
-import java.util.function.Supplier;
-
 import org.neo4j.internal.kernel.api.CursorFactory;
 import org.neo4j.internal.kernel.api.Kernel;
 import org.neo4j.internal.kernel.api.security.SecurityContext;
 import org.neo4j.kernel.api.InwardKernel;
-import org.neo4j.kernel.api.txstate.ExplicitIndexTransactionState;
 import org.neo4j.storageengine.api.StorageEngine;
 import org.neo4j.storageengine.api.StorageStatement;
 
@@ -48,7 +45,6 @@ public NewKernel( StorageEngine engine, InwardKernel kernel )
         this.engine = engine;
         this.kernel = kernel;
         this.isRunning = false;
-        this.cursors = new Cursors(  );
     }
 
     @Override
@@ -80,5 +76,6 @@ public void stop()
         }
         statement.close();
         isRunning = false;
+        this.cursors = null;
     }
 }

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

@@ -271,6 +271,9 @@ public void close()
             pageCursor.close();
             pageCursor = null;
         }
+        read = null;
+        labelCursor = null;
+
         reset();
     }
 

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

@@ -89,6 +89,7 @@ public void close()
         node = NO_ID;
         score = 0;
         expectedSize = 0;
+        read = null;
     }
 
     @Override

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

@@ -81,6 +81,7 @@ public void close()
         super.close();
         node = NO_ID;
         labels = null;
+        read = null;
     }
 
     @Override

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

@@ -102,6 +102,7 @@ public void close()
         this.node = NO_ID;
         this.keys = null;
         this.values = null;
+        this.read = null;
     }
 
     @Override

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

@@ -367,7 +367,7 @@ public boolean nodeDelete( long node ) throws AutoIndexingKernelException
         }
 
         ktx.locks().optimistic().acquireExclusive( ktx.lockTracer(), ResourceTypes.NODE, node );
-        if ( allStoreHolder.nodeExists( node ) )
+        if ( allStoreHolder.nodeExistsInStore( node ) )
         {
             autoIndexing.nodes().entityRemoved( this, node );
             ktx.txState().nodeDoDelete( node );

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

@@ -196,6 +196,7 @@ public void close()
         propertiesState = null;
         changedProperties = null;
         stateValue = null;
+        read = null;
         clear();
     }
 

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

@@ -25,7 +25,6 @@
 import org.neo4j.internal.kernel.api.CapableIndexReference;
 import org.neo4j.internal.kernel.api.IndexOrder;
 import org.neo4j.internal.kernel.api.IndexQuery;
-import org.neo4j.internal.kernel.api.RelationshipExplicitIndexCursor;
 import org.neo4j.internal.kernel.api.Scan;
 import org.neo4j.internal.kernel.api.exceptions.KernelException;
 import org.neo4j.io.pagecache.PageCursor;
@@ -165,7 +164,7 @@ public final Scan<org.neo4j.internal.kernel.api.NodeLabelIndexCursor> nodeLabelS
     @Override
     public final void allNodesScan( org.neo4j.internal.kernel.api.NodeCursor cursor )
     {
-        ((NodeCursor) cursor).scan(this);
+        ((NodeCursor) cursor).scan( this );
     }
 
     @Override
@@ -319,52 +318,52 @@ public final void nodeExplicitIndexQuery(
             org.neo4j.internal.kernel.api.NodeExplicitIndexCursor cursor, String index, String key, Object query ) throws KernelException
     {
         ((NodeExplicitIndexCursor) cursor).setRead( this );
-        explicitIndex( (org.neo4j.kernel.impl.newapi.NodeExplicitIndexCursor) cursor, explicitNodeIndex( index ).query(
+        explicitIndex( (NodeExplicitIndexCursor) cursor, explicitNodeIndex( index ).query(
                 key, query instanceof Value ? ((Value) query).asObject() : query ) );
     }
 
     @Override
     public void relationshipExplicitIndexGet(
-            RelationshipExplicitIndexCursor cursor,
+            org.neo4j.internal.kernel.api.RelationshipExplicitIndexCursor cursor,
             String index,
             String key,
             Value value,
             long source,
             long target ) throws KernelException
     {
-        ((org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor).setRead( this );
+        ((RelationshipExplicitIndexCursor) cursor).setRead( this );
         explicitIndex(
-                (org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor,
+                (RelationshipExplicitIndexCursor) cursor,
                 explicitRelationshipIndex( index ).get( key, value.asObject(), source, target ) );
     }
 
     @Override
     public void relationshipExplicitIndexQuery(
-            RelationshipExplicitIndexCursor cursor,
+            org.neo4j.internal.kernel.api.RelationshipExplicitIndexCursor cursor,
             String index,
             Object query,
             long source,
             long target ) throws KernelException
     {
-        ((org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor).setRead( this );
+        ((RelationshipExplicitIndexCursor) cursor).setRead( this );
         explicitIndex(
-                (org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor,
+                (RelationshipExplicitIndexCursor) cursor,
                 explicitRelationshipIndex( index )
                         .query( query instanceof Value ? ((Value) query).asObject() : query, source, target ) );
     }
 
     @Override
     public void relationshipExplicitIndexQuery(
-            RelationshipExplicitIndexCursor cursor,
+            org.neo4j.internal.kernel.api.RelationshipExplicitIndexCursor cursor,
             String index,
             String key,
             Object query,
             long source,
             long target ) throws KernelException
     {
-        ((org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor).setRead( this );
+        ((RelationshipExplicitIndexCursor) cursor).setRead( this );
         explicitIndex(
-                (org.neo4j.kernel.impl.newapi.RelationshipExplicitIndexCursor) cursor,
+                (RelationshipExplicitIndexCursor) cursor,
                 explicitRelationshipIndex( index ).query(
                         key, query instanceof Value ? ((Value) query).asObject() : query, source, target ) );
     }

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

@@ -115,6 +115,7 @@ public void close()
         relationship = NO_ID;
         score = 0;
         expectedSize = 0;
+        read = null;
     }
 
     @Override

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

@@ -159,6 +159,7 @@ public void close()
             edgePage = null;
         }
         current = null;
+        read = null;
         setId( NO_ID );
         clear();
     }

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

@@ -111,6 +111,7 @@ public void close()
             pageCursor.close();
             pageCursor = null;
         }
+        read = null;
         reset();
     }
 

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

@@ -425,6 +425,7 @@ public void close()
             pageCursor.close();
             pageCursor = null;
         }
+        read = null;
         reset();
     }
 

community/kernel/src/test/java/org/neo4j/kernel/impl/api/KernelTransactionTerminationTest.java

@@ -343,8 +343,9 @@ private static class TestKernelTransaction extends KernelTransactionImplementati
                     mock( Pool.class ), Clocks.fakeClock(), CpuClock.NOT_AVAILABLE, HeapAllocation.NOT_AVAILABLE,
                     TransactionTracer.NULL,
                     LockTracer.NONE, PageCursorTracerSupplier.NULL,
-                            mock( StorageEngine.class, RETURNS_MOCKS ), new CanWrite(), mock(Cursors.class), AutoIndexing.UNSUPPORTED, mock(
-                            ExplicitIndexStore.class) );
+                    mock( StorageEngine.class, RETURNS_MOCKS ), new CanWrite(), mock( Cursors.class ),
+                    AutoIndexing.UNSUPPORTED, mock(
+                            ExplicitIndexStore.class ) );
 
             this.monitor = monitor;
         }

community/kernel/src/test/java/org/neo4j/kernel/impl/newapi/OperationsLockTest.java

@@ -190,7 +190,7 @@ public void shouldAcquireEntityWriteLockBeforeDeletingNode()
         // GIVEN
         when( nodeCursor.next() ).thenReturn( true );
         when( nodeCursor.labels() ).thenReturn( LabelSet.NONE );
-        when( allStoreHolder.nodeExists( 123 ) ).thenReturn( true );
+        when( allStoreHolder.nodeExistsInStore( 123 ) ).thenReturn( true );
 
         // WHEN
         operations.nodeDelete(  123 );