Less index updates work sync if no relevant updates

by figuring out if there are any potential updates at all and if not
skip creating a couple of update instances and participating in index/label
work sync jobs unnecessarily.

community/kernel/src/main/java/org/neo4j/kernel/impl/api/index/NodePropertyCommandsExtractor.java

@@ -34,6 +34,7 @@
 import org.neo4j.storageengine.api.CommandsToApply;
 
 import static org.neo4j.collection.primitive.Primitive.longObjectMap;
+import static org.neo4j.kernel.impl.store.NodeLabelsField.fieldPointsToDynamicRecordOfLabels;
 
 /**
  * Implements both BatchTransactionApplier and TransactionApplier in order to reduce garbage.
@@ -44,6 +45,7 @@ public class NodePropertyCommandsExtractor extends TransactionApplier.Adapter
 {
     private final PrimitiveLongObjectMap<NodeCommand> nodeCommandsById = longObjectMap();
     private final PrimitiveLongObjectMap<List<PropertyCommand>> propertyCommandsByNodeIds = longObjectMap();
+    private boolean hasUpdates;
 
     @Override
     public TransactionApplier startTx( CommandsToApply transaction )
@@ -68,9 +70,24 @@ public void close() throws Exception
     public boolean visitNodeCommand( NodeCommand command ) throws IOException
     {
         nodeCommandsById.put( command.getKey(), command );
+        if ( !hasUpdates && hasLabelChanges( command ) )
+        {
+            hasUpdates = true;
+        }
         return false;
     }
 
+    private boolean hasLabelChanges( NodeCommand command )
+    {
+        long before = command.getBefore().getLabelField();
+        long after = command.getAfter().getLabelField();
+        return before != after ||
+                // Because we don't know here, there may have been changes to a dynamic label record
+                // even though it still points to the same one
+                fieldPointsToDynamicRecordOfLabels( before ) || fieldPointsToDynamicRecordOfLabels( after );
+
+    }
+
     @Override
     public boolean visitPropertyCommand( PropertyCommand command ) throws IOException
     {
@@ -84,13 +101,14 @@ public boolean visitPropertyCommand( PropertyCommand command ) throws IOExceptio
                 propertyCommandsByNodeIds.put( nodeId, group = new ArrayList<>() );
             }
             group.add( command );
+            hasUpdates = true;
         }
         return false;
     }
 
     public boolean containsAnyNodeOrPropertyUpdate()
     {
-        return !nodeCommandsById.isEmpty() || !propertyCommandsByNodeIds.isEmpty();
+        return hasUpdates;
     }
 
     public PrimitiveLongObjectMap<NodeCommand> nodeCommandsById()

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/command/IndexBatchTransactionApplier.java

@@ -83,7 +83,7 @@ public TransactionApplier startTx( CommandsToApply transaction )
 
     private void applyIndexUpdates()
     {
-        if ( indexUpdates != null )
+        if ( indexUpdates != null && indexUpdates.hasUpdates() )
         {
             indexUpdatesSync.apply( new IndexUpdatesWork( indexUpdates ) );
             indexUpdates = null;

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/command/IndexUpdatesWork.java

@@ -100,6 +100,12 @@ public void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,
             {
                 throw new UnsupportedOperationException();
             }
+
+            @Override
+            public boolean hasUpdates()
+            {
+                return true;
+            }
         };
     }
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/state/DirectIndexUpdates.java

@@ -58,4 +58,10 @@ public void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,
     {
         throw new UnsupportedOperationException();
     }
+
+    @Override
+    public boolean hasUpdates()
+    {
+        return true;
+    }
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/state/IndexUpdates.java

@@ -49,4 +49,6 @@ void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,
      * @param target to receive these node ids.
      */
     void collectUpdatedNodeIds( PrimitiveLongSet target );
+
+    boolean hasUpdates();
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/state/OnlineIndexUpdates.java

@@ -96,6 +96,12 @@ public void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propertyCommands
         gatherUpdatesFromNodeCommands( nodeCommands, propertyCommands, propertyChanges );
     }
 
+    @Override
+    public boolean hasUpdates()
+    {
+        return !updates.isEmpty();
+    }
+
     private void gatherUpdatesFromPropertyCommands(
             PrimitiveLongObjectMap<NodeCommand> nodeCommands,
             PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,

community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/state/RecoveryIndexUpdates.java

@@ -57,4 +57,10 @@ public void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,
         ids.addAll( propCommands.iterator() );
         ids.addAll( nodeCommands.iterator() );
     }
+
+    @Override
+    public boolean hasUpdates()
+    {
+        return !ids.isEmpty();
+    }
 }

community/kernel/src/test/java/org/neo4j/kernel/impl/api/index/IndexingServiceTest.java

@@ -717,6 +717,12 @@ public void feed( PrimitiveLongObjectMap<List<PropertyCommand>> propCommands,
             {
                 throw new UnsupportedOperationException();
             }
+
+            @Override
+            public boolean hasUpdates()
+            {
+                return !nodeIds.isEmpty();
+            }
         };
     }