Specific TxStateVisitor.Decorator interface

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

@@ -21,7 +21,7 @@
 
 import org.eclipse.collections.api.iterator.LongIterator;
 import org.eclipse.collections.api.set.primitive.MutableLongSet;
-import org.eclipse.collections.impl.factory.primitive.LongSets;
+import org.eclipse.collections.impl.iterator.ImmutableEmptyLongIterator;
 import org.eclipse.collections.impl.set.mutable.primitive.LongHashSet;
 
 import org.neo4j.internal.kernel.api.LabelSet;
@@ -57,7 +57,7 @@ void scan( Read read )
         this.read = read;
         this.single = NO_ID;
         this.hasChanges = HasChanges.MAYBE;
-        this.addedNodes = LongSets.immutable.empty().longIterator();
+        this.addedNodes = ImmutableEmptyLongIterator.INSTANCE;
     }
 
     void single( long reference, Read read )
@@ -66,7 +66,7 @@ void single( long reference, Read read )
         this.read = read;
         this.single = reference;
         this.hasChanges = HasChanges.MAYBE;
-        this.addedNodes = LongSets.immutable.empty().longIterator();
+        this.addedNodes = ImmutableEmptyLongIterator.INSTANCE;
     }
 
     @Override
@@ -199,7 +199,7 @@ public void close()
         {
             read = null;
             hasChanges = HasChanges.MAYBE;
-            addedNodes = LongSets.immutable.empty().longIterator();
+            addedNodes = ImmutableEmptyLongIterator.INSTANCE;
             storeCursor.close();
 
             pool.accept( this );
@@ -227,7 +227,7 @@ private boolean hasChanges()
                 if ( single != NO_ID )
                 {
                     addedNodes = read.txState().nodeIsAddedInThisTx( single ) ?
-                                 LongHashSet.newSetWith( single ).longIterator() : LongSets.immutable.empty().longIterator();
+                                 LongHashSet.newSetWith( single ).longIterator() : ImmutableEmptyLongIterator.INSTANCE;
                 }
                 else
                 {

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

@@ -20,7 +20,7 @@
 package org.neo4j.kernel.impl.newapi;
 
 import org.eclipse.collections.api.iterator.LongIterator;
-import org.eclipse.collections.impl.factory.primitive.LongSets;
+import org.eclipse.collections.impl.iterator.ImmutableEmptyLongIterator;
 import org.eclipse.collections.impl.set.mutable.primitive.LongHashSet;
 
 import org.neo4j.internal.kernel.api.RelationshipScanCursor;
@@ -45,7 +45,7 @@ void scan( int type, Read read )
         this.type = type;
         this.single = NO_ID;
         init( read );
-        this.addedRelationships = LongSets.immutable.empty().longIterator();
+        this.addedRelationships = ImmutableEmptyLongIterator.INSTANCE;
     }
 
     void single( long reference, Read read )
@@ -54,7 +54,7 @@ void single( long reference, Read read )
         type = -1;
         this.single = reference;
         init( read );
-        this.addedRelationships = LongSets.immutable.empty().longIterator();
+        this.addedRelationships = ImmutableEmptyLongIterator.INSTANCE;
     }
 
     @Override
@@ -119,7 +119,7 @@ protected void collectAddedTxStateSnapshot()
         {
             addedRelationships = read.txState().relationshipIsAddedInThisTx( single )
                                  ? LongHashSet.newSetWith( single ).longIterator()
-                                 : LongSets.immutable.empty().longIterator();
+                                 : ImmutableEmptyLongIterator.INSTANCE;
         }
         else
         {

community/kernel/src/main/java/org/neo4j/kernel/impl/storageengine/impl/recordstorage/RecordStorageEngine.java

@@ -24,7 +24,6 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.function.Function;
 import java.util.function.Supplier;
 
 import org.neo4j.graphdb.factory.GraphDatabaseSettings;
@@ -267,7 +266,7 @@ public CommandReaderFactory commandReaderFactory()
     @SuppressWarnings( "resource" )
     @Override
     public void createCommands( Collection<StorageCommand> commands, ReadableTransactionState txState, StorageReader storageReader, ResourceLocker locks,
-            long lastTransactionIdWhenStarted, Function<TxStateVisitor,TxStateVisitor> additionalTxStateVisitor )
+            long lastTransactionIdWhenStarted, TxStateVisitor.Decorator additionalTxStateVisitor )
             throws TransactionFailureException, CreateConstraintFailureException, ConstraintValidationException
     {
         if ( txState != null )

community/kernel/src/main/java/org/neo4j/storageengine/api/StorageEngine.java

@@ -20,7 +20,6 @@
 package org.neo4j.storageengine.api;
 
 import java.util.Collection;
-import java.util.function.Function;
 import java.util.stream.Stream;
 
 import org.neo4j.internal.kernel.api.exceptions.TransactionFailureException;
@@ -49,7 +48,7 @@ public interface StorageEngine
 
     /**
      * @return a new {@link CommandCreationContext} meant to be kept for multiple calls to
-     * {@link #createCommands(Collection, ReadableTransactionState, StorageReader, ResourceLocker, long, Function)}.
+     * {@link #createCommands(Collection, ReadableTransactionState, StorageReader, ResourceLocker, long, TxStateVisitor.Decorator)}.
      * Must be {@link CommandCreationContext#close() closed} after used, before being discarded.
      */
     CommandCreationContext allocateCommandCreationContext();
@@ -87,7 +86,7 @@ void createCommands(
             StorageReader storageReader,
             ResourceLocker locks,
             long lastTransactionIdWhenStarted,
-            Function<TxStateVisitor,TxStateVisitor> additionalTxStateVisitor )
+            TxStateVisitor.Decorator additionalTxStateVisitor )
             throws TransactionFailureException, CreateConstraintFailureException, ConstraintValidationException;
 
     /**

community/kernel/src/main/java/org/neo4j/storageengine/api/txstate/TxStateVisitor.java

@@ -23,6 +23,7 @@
 import org.eclipse.collections.api.set.primitive.LongSet;
 
 import java.util.Iterator;
+import java.util.function.Function;
 
 import org.neo4j.internal.kernel.api.exceptions.schema.ConstraintValidationException;
 import org.neo4j.internal.kernel.api.schema.constraints.ConstraintDescriptor;
@@ -272,4 +273,13 @@ public void close()
             actual.close();
         }
     }
+
+    /**
+     * Interface for allowing decoration of a TxStateVisitor with one or more other visitor(s).
+     */
+    interface Decorator extends Function<TxStateVisitor,TxStateVisitor>
+    {
+    }
+
+    Decorator NO_DECORATION = txStateVisitor -> txStateVisitor;
 }

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

@@ -33,7 +33,6 @@
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
-import java.util.function.Function;
 
 import org.neo4j.graphdb.TransactionTerminatedException;
 import org.neo4j.internal.kernel.api.exceptions.TransactionFailureException;
@@ -54,6 +53,7 @@
 import org.neo4j.storageengine.api.StorageCommand;
 import org.neo4j.storageengine.api.StorageReader;
 import org.neo4j.storageengine.api.lock.ResourceLocker;
+import org.neo4j.storageengine.api.txstate.TxStateVisitor;
 import org.neo4j.test.DoubleLatch;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
@@ -382,7 +382,7 @@ public void shouldUseStartTimeAndTxIdFromWhenStartingTxAsHeader() throws Excepti
                 any( TransactionState.class ),
                 any( StorageReader.class ),
                 any( ResourceLocker.class ),
-                anyLong(), any( Function.class ) );
+                anyLong(), any( TxStateVisitor.Decorator.class ) );
 
         try ( KernelTransactionImplementation transaction = newTransaction( loginContext() ) )
         {

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

@@ -28,7 +28,6 @@
 
 import java.util.Collection;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.Function;
 import java.util.function.Supplier;
 
 import org.neo4j.collection.pool.Pool;
@@ -71,6 +70,7 @@
 import org.neo4j.storageengine.api.TransactionApplicationMode;
 import org.neo4j.storageengine.api.lock.ResourceLocker;
 import org.neo4j.storageengine.api.txstate.ReadableTransactionState;
+import org.neo4j.storageengine.api.txstate.TxStateVisitor;
 import org.neo4j.time.Clocks;
 import org.neo4j.time.FakeClock;
 
@@ -119,7 +119,7 @@ public void before() throws Exception
                     any( ReadableTransactionState.class ),
                     any( StorageReader.class ), any( ResourceLocker.class ),
                     anyLong(),
-                    any( Function.class ) );
+                    any( TxStateVisitor.Decorator.class ) );
     }
 
     public KernelTransactionImplementation newTransaction( long transactionTimeoutMillis )

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

@@ -32,7 +32,6 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.atomic.AtomicReferenceArray;
-import java.util.function.Function;
 
 import org.neo4j.graphdb.DatabaseShutdownException;
 import org.neo4j.graphdb.security.AuthorizationExpiredException;
@@ -78,6 +77,7 @@
 import org.neo4j.storageengine.api.TransactionApplicationMode;
 import org.neo4j.storageengine.api.lock.ResourceLocker;
 import org.neo4j.storageengine.api.txstate.ReadableTransactionState;
+import org.neo4j.storageengine.api.txstate.TxStateVisitor;
 import org.neo4j.test.OtherThreadExecutor;
 import org.neo4j.test.Race;
 import org.neo4j.test.rule.concurrent.OtherThreadRule;
@@ -564,7 +564,8 @@ private static KernelTransactions newKernelTransactions( boolean testKernelTrans
                 any( ReadableTransactionState.class ),
                 any( StorageReader.class ),
                 any( ResourceLocker.class ),
-                anyLong(), any( Function.class ) );
+                anyLong(),
+                any( TxStateVisitor.Decorator.class ) );
 
         return newKernelTransactions( locks, storageEngine, commitProcess, testKernelTransactions );
     }

community/kernel/src/test/java/org/neo4j/kernel/impl/transaction/command/IndexWorkSyncTransactionApplicationStressIT.java

@@ -61,13 +61,13 @@
 import org.neo4j.values.storable.Values;
 
 import static java.util.Collections.singletonList;
-import static java.util.function.Function.identity;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.neo4j.helpers.TimeUtil.parseTimeMillis;
 import static org.neo4j.kernel.impl.transaction.command.Commands.createIndexRule;
 import static org.neo4j.kernel.impl.transaction.command.Commands.transactionRepresentation;
 import static org.neo4j.kernel.impl.transaction.log.Commitment.NO_COMMITMENT;
+import static org.neo4j.storageengine.api.txstate.TxStateVisitor.NO_DECORATION;
 
 public class IndexWorkSyncTransactionApplicationStressIT
 {
@@ -205,7 +205,7 @@ private TransactionToApply createNodeAndProperty( int progress ) throws Exceptio
             Collection<StorageCommand> commands = new ArrayList<>();
             try ( StorageReader statement = storageEngine.newReader() )
             {
-                storageEngine.createCommands( commands, txState, statement, null, 0, identity() );
+                storageEngine.createCommands( commands, txState, statement, null, 0, NO_DECORATION );
             }
             return tx( commands );
         }

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/core/state/machines/token/ReplicatedTokenHolder.java

@@ -47,7 +47,7 @@
 import org.neo4j.storageengine.api.Token;
 import org.neo4j.storageengine.api.lock.ResourceLocker;
 
-import static java.util.function.Function.identity;
+import static org.neo4j.storageengine.api.txstate.TxStateVisitor.NO_DECORATION;
 
 abstract class ReplicatedTokenHolder<TOKEN extends Token> implements TokenHolder<TOKEN>
 {
@@ -133,7 +133,7 @@ private byte[] createCommands( String tokenName )
         createToken( txState, tokenName, tokenId );
         try ( StorageReader statement = storageEngine.newReader() )
         {
-            storageEngine.createCommands( commands, txState, statement, ResourceLocker.NONE, Long.MAX_VALUE, identity() );
+            storageEngine.createCommands( commands, txState, statement, ResourceLocker.NONE, Long.MAX_VALUE, NO_DECORATION );
         }
         catch ( CreateConstraintFailureException | TransactionFailureException | ConstraintValidationException e )
         {

enterprise/causal-clustering/src/test/java/org/neo4j/causalclustering/core/state/machines/token/ReplicatedTokenHolderTest.java

@@ -26,7 +26,6 @@
 
 import java.util.Collection;
 import java.util.concurrent.CompletableFuture;
-import java.util.function.Function;
 
 import org.neo4j.kernel.impl.store.id.IdGenerator;
 import org.neo4j.kernel.impl.store.id.IdGeneratorFactory;
@@ -140,7 +139,7 @@ public void visitCreatedLabelToken( long id, String name )
             } );
             return null;
         } ).when( storageEngine ).createCommands( anyCollection(), any( ReadableTransactionState.class ),
-                any( StorageReader.class ), any( ResourceLocker.class ), anyLong(), any( Function.class ) );
+                any( StorageReader.class ), any( ResourceLocker.class ), anyLong(), any( TxStateVisitor.Decorator.class ) );
 
         StorageReader readLayer = mock( StorageReader.class );
         when( storageEngine.newReader() ).thenReturn( readLayer );