Label scan store is no longer a kernel extension

As there is only one label scan store implementation
there is no need to keep it around as a kernel extension.

Remove
 - LabelScanStoreProvider
 - NativeLabelScanStoreExtension
 - LabelIndex enum in settings

Instead of being loaded as a kernel extension label scan store
is constructed in RecordStorageEngine.

DynamicIndexStoreView that decorate NeoStoreIndexStoreView
with the possibility to utilize LabelScanStore for some operations
used to do this by extending NeoStoreIndexStoreView. This
created a circular dependency that went like

LabelScanStore -> FullLabelStream -> IndexStoreView -> LabelScanStore

This dependency is broken apart by letting DynamicIndexStoreView
delegate to NeoStoreIndexStoreView instead of extending it.
This makes it possible for NativeLabelScanStore to use
NeoStoreIndexStoreView instead of DynamicIndexStoreView.

community/consistency-check/src/main/java/org/neo4j/consistency/ConsistencyCheckService.java

@@ -36,7 +36,6 @@
 import org.neo4j.consistency.statistics.VerboseStatistics;
 import org.neo4j.function.Suppliers;
 import org.neo4j.graphdb.factory.GraphDatabaseSettings;
-import org.neo4j.graphdb.factory.GraphDatabaseSettings.LabelIndex;
 import org.neo4j.helpers.progress.ProgressMonitorFactory;
 import org.neo4j.index.internal.gbptree.RecoveryCleanupWorkCollector;
 import org.neo4j.io.fs.DefaultFileSystemAbstraction;
@@ -52,9 +51,9 @@
 import org.neo4j.kernel.extension.KernelExtensions;
 import org.neo4j.kernel.extension.dependency.HighestSelectionStrategy;
 import org.neo4j.kernel.impl.api.index.IndexStoreView;
-import org.neo4j.kernel.impl.api.scan.LabelScanStoreProvider;
+import org.neo4j.kernel.impl.api.scan.FullStoreChangeStream;
+import org.neo4j.kernel.impl.index.labelscan.NativeLabelScanStore;
 import org.neo4j.kernel.impl.locking.LockService;
-import org.neo4j.kernel.impl.logging.SimpleLogService;
 import org.neo4j.kernel.impl.pagecache.ConfiguringPageCacheFactory;
 import org.neo4j.kernel.impl.spi.KernelContext;
 import org.neo4j.kernel.impl.spi.SimpleKernelContext;
@@ -194,7 +193,7 @@ public Result runFullConsistencyCheck( final File storeDir, Config config, Progr
             final boolean verbose, CheckConsistencyConfig checkConsistencyConfig )
             throws ConsistencyCheckIncompleteException
     {
-        return runFullConsistencyCheck( storeDir,  config, progressFactory, logProvider, fileSystem, pageCache,
+        return runFullConsistencyCheck( storeDir, config, progressFactory, logProvider, fileSystem, pageCache,
                 verbose, defaultReportDir( config, storeDir ), checkConsistencyConfig );
     }
 
@@ -215,8 +214,7 @@ public Result runFullConsistencyCheck( final File storeDir, Config config, Progr
     {
         Log log = logProvider.getLog( getClass() );
         config = config.with( stringMap(
-                GraphDatabaseSettings.read_only.name(), TRUE,
-                GraphDatabaseSettings.label_index.name(), LabelIndex.AUTO.name() ) );
+                GraphDatabaseSettings.read_only.name(), TRUE ) );
         StoreFactory factory = new StoreFactory( storeDir, config,
                 new DefaultIdGeneratorFactory( fileSystem ), pageCache, fileSystem, logProvider );
 
@@ -240,16 +238,18 @@ public Result runFullConsistencyCheck( final File storeDir, Config config, Progr
         {
             IndexStoreView indexStoreView = new NeoStoreIndexStoreView( LockService.NO_LOCK_SERVICE, neoStores );
             Dependencies dependencies = new Dependencies();
-            dependencies.satisfyDependencies( config, fileSystem, new SimpleLogService( logProvider, logProvider ),
-                    indexStoreView, pageCache, new Monitors(), RecoveryCleanupWorkCollector.IMMEDIATE );
             KernelContext kernelContext = new SimpleKernelContext( storeDir, UNKNOWN, dependencies );
             KernelExtensions extensions = life.add( new KernelExtensions(
                     kernelContext, (Iterable) load( KernelExtensionFactory.class ), dependencies, ignore() ) );
             life.start();
-            LabelScanStore labelScanStore = life.add( extensions.resolveDependency( LabelScanStoreProvider.class ).getLabelScanStore() );
             SchemaIndexProvider indexes = life.add( extensions.resolveDependency( SchemaIndexProvider.class,
                     HighestSelectionStrategy.getInstance() ) );
 
+            LabelScanStore labelScanStore =
+                    new NativeLabelScanStore( pageCache, storeDir, FullStoreChangeStream.EMPTY, true, new Monitors(),
+                            RecoveryCleanupWorkCollector.IMMEDIATE );
+            life.add( labelScanStore );
+
             int numberOfThreads = defaultConsistencyCheckThreadsNumber();
             Statistics statistics;
             StoreAccess storeAccess;

community/consistency-check/src/test/java/org/neo4j/consistency/checking/GraphStoreFixture.java

@@ -50,17 +50,13 @@
 import org.neo4j.kernel.api.index.SchemaIndexProvider;
 import org.neo4j.kernel.api.labelscan.LabelScanStore;
 import org.neo4j.kernel.configuration.Config;
-import org.neo4j.kernel.extension.KernelExtensionFactory;
-import org.neo4j.kernel.extension.KernelExtensions;
 import org.neo4j.kernel.impl.api.TransactionRepresentationCommitProcess;
 import org.neo4j.kernel.impl.api.TransactionToApply;
 import org.neo4j.kernel.impl.api.index.IndexStoreView;
-import org.neo4j.kernel.impl.api.scan.LabelScanStoreProvider;
+import org.neo4j.kernel.impl.api.scan.FullLabelStream;
 import org.neo4j.kernel.impl.factory.OperationalMode;
+import org.neo4j.kernel.impl.index.labelscan.NativeLabelScanStore;
 import org.neo4j.kernel.impl.locking.LockService;
-import org.neo4j.kernel.impl.logging.SimpleLogService;
-import org.neo4j.kernel.impl.spi.KernelContext;
-import org.neo4j.kernel.impl.spi.SimpleKernelContext;
 import org.neo4j.kernel.impl.storageengine.impl.recordstorage.RecordStorageEngine;
 import org.neo4j.kernel.impl.store.NeoStores;
 import org.neo4j.kernel.impl.store.NodeLabelsField;
@@ -78,9 +74,7 @@
 import org.neo4j.kernel.impl.transaction.log.TransactionIdStore;
 import org.neo4j.kernel.impl.transaction.state.storeview.NeoStoreIndexStoreView;
 import org.neo4j.kernel.impl.transaction.tracing.CommitEvent;
-import org.neo4j.kernel.impl.util.Dependencies;
 import org.neo4j.kernel.internal.GraphDatabaseAPI;
-import org.neo4j.kernel.lifecycle.LifeSupport;
 import org.neo4j.kernel.monitoring.Monitors;
 import org.neo4j.logging.FormattedLogProvider;
 import org.neo4j.logging.LogProvider;
@@ -95,9 +89,6 @@
 
 import static java.lang.System.currentTimeMillis;
 import static org.neo4j.consistency.ConsistencyCheckService.defaultConsistencyCheckThreadsNumber;
-import static org.neo4j.helpers.Service.load;
-import static org.neo4j.kernel.extension.UnsatisfiedDependencyStrategies.ignore;
-import static org.neo4j.kernel.impl.factory.DatabaseInfo.UNKNOWN;
 
 public abstract class GraphStoreFixture extends ConfigurablePageCacheRule implements TestRule
 {
@@ -187,29 +178,18 @@ public DirectStoreAccess directStoreAccess()
                     new NeoStoreIndexStoreView( LockService.NO_LOCK_SERVICE, nativeStores.getRawNeoStores() );
             RecoveryCleanupWorkCollector recoveryCleanupWorkCollector = RecoveryCleanupWorkCollector.IMMEDIATE;
 
-            Dependencies dependencies = new Dependencies();
-            dependencies.satisfyDependencies( Config.defaults(), fileSystem,
-                    new SimpleLogService( logProvider, logProvider ), indexStoreView, pageCache, new Monitors(),
-                    recoveryCleanupWorkCollector );
-            KernelContext kernelContext = new SimpleKernelContext( directory, UNKNOWN, dependencies );
-            LabelScanStore labelScanStore = startLabelScanStore( config, dependencies, kernelContext );
+            LabelScanStore labelScanStore = startLabelScanStore( pageCache, indexStoreView );
             directStoreAccess = new DirectStoreAccess( nativeStores, labelScanStore, createIndexes( fileSystem,
                     config, operationalMode ) );
         }
         return directStoreAccess;
     }
 
-    private LabelScanStore startLabelScanStore( Config config, Dependencies dependencies, KernelContext kernelContext )
+    private LabelScanStore startLabelScanStore( PageCache pageCache, IndexStoreView indexStoreView )
     {
-        // Load correct LSS from kernel extensions
-        LifeSupport life = new LifeSupport();
-        KernelExtensions extensions = life.add( new KernelExtensions(
-                kernelContext, (Iterable) load( KernelExtensionFactory.class ), dependencies, ignore() ) );
-        life.start();
-        LabelScanStore labelScanStore = extensions.resolveDependency( LabelScanStoreProvider.class ).getLabelScanStore();
-        life.shutdown();
-
-        // Start the selected LSS
+        NativeLabelScanStore labelScanStore =
+                new NativeLabelScanStore( pageCache, directory, new FullLabelStream( indexStoreView ), false, new Monitors(),
+                        RecoveryCleanupWorkCollector.IMMEDIATE );
         try
         {
             labelScanStore.init();

community/kernel/src/main/java/org/neo4j/graphdb/factory/GraphDatabaseSettings.java

@@ -45,7 +45,6 @@
 import org.neo4j.kernel.impl.cache.MonitorGc;
 import org.neo4j.logging.Level;
 
-import static org.neo4j.helpers.collection.Iterables.enumNames;
 import static org.neo4j.kernel.configuration.Settings.ANY;
 import static org.neo4j.kernel.configuration.Settings.BOOLEAN;
 import static org.neo4j.kernel.configuration.Settings.BYTES;
@@ -544,23 +543,11 @@ public class GraphDatabaseSettings implements LoadableConfig
     public static final Setting<Integer> batch_inserter_batch_size = setting( "unsupported.tools.batch_inserter.batch_size", INTEGER,
             "10000" );
 
-    public enum LabelIndex
-    {
-        /**
-         * Native label index. Generally the best option.
-         */
-        NATIVE,
-
-        /**
-         * Selects which ever label index is present in a store, or the default (NATIVE) if no label index present.
-         */
-        AUTO
-    }
-
+    // todo Can we simply remove this setting or do we need to depricate it?
+    @Deprecated
     @Description( "Backend to use for label --> nodes index" )
     @Internal
-    public static final Setting<String> label_index = setting( "dbms.label_index",
-            options( enumNames( LabelIndex.class ), true ), LabelIndex.NATIVE.name() );
+    public static final Setting<String> label_index = setting( "dbms.label_index", STRING, "native" );
 
     // Security settings
 

community/kernel/src/main/java/org/neo4j/kernel/NeoStoreDataSource.java

@@ -68,7 +68,6 @@
 import org.neo4j.kernel.impl.api.TransactionHooks;
 import org.neo4j.kernel.impl.api.index.IndexingService;
 import org.neo4j.kernel.impl.api.operations.QueryRegistrationOperations;
-import org.neo4j.kernel.impl.api.scan.LabelScanStoreProvider;
 import org.neo4j.kernel.impl.api.state.ConstraintIndexCreator;
 import org.neo4j.kernel.impl.constraints.ConstraintSemantics;
 import org.neo4j.kernel.impl.core.LabelTokenHolder;
@@ -267,7 +266,6 @@ boolean applicable( DiagnosticsPhase phase )
     private Dependencies dependencies;
     private LifeSupport life;
     private SchemaIndexProvider schemaIndexProvider;
-    private LabelScanStoreProvider labelScanStoreProvider;
     private File storeDir;
     private boolean readOnly;
     private final IdController idController;
@@ -408,8 +406,6 @@ public void start() throws IOException
                 HighestSelectionStrategy.getInstance() );
         dependencies.satisfyDependency( schemaIndexProvider );
 
-        labelScanStoreProvider = dependencyResolver.resolveDependency( LabelScanStoreProvider.class );
-
         IndexConfigStore indexConfigStore = new IndexConfigStore( storeDir, fs );
         dependencies.satisfyDependency( lockService );
         dependencies.satisfyDependency( indexConfigStore );
@@ -558,7 +554,6 @@ private void upgradeStore( RecordFormats format )
                 config,
                 logService,
                 schemaIndexProvider,
-                labelScanStoreProvider,
                 indexProviders,
                 pageCache,
                 format ).migrate( storeDir );
@@ -574,8 +569,8 @@ private StorageEngine buildStorageEngine(
                 new RecordStorageEngine( storeDir, config, pageCache, fs, logProvider, propertyKeyTokenHolder,
                         labelTokens, relationshipTypeTokens, schemaState, constraintSemantics, scheduler,
                         tokenNameLookup, lockService, schemaIndexProvider, indexingServiceMonitor, databaseHealth,
-                        labelScanStoreProvider, legacyIndexProviderLookup, indexConfigStore,
-                        legacyIndexTransactionOrdering, idGeneratorFactory, idController );
+                        legacyIndexProviderLookup, indexConfigStore,
+                        legacyIndexTransactionOrdering, idGeneratorFactory, idController, monitors, recoveryCleanupWorkCollector );
 
         // We pretend that the storage engine abstract hides all details within it. Whereas that's mostly
         // true it's not entirely true for the time being. As long as we need this call below, which

community/kernel/src/main/java/org/neo4j/kernel/api/index/SchemaIndexProvider.java

@@ -29,7 +29,6 @@
 import org.neo4j.kernel.api.schema.index.IndexDescriptor;
 import org.neo4j.kernel.impl.api.index.IndexingService;
 import org.neo4j.kernel.impl.api.index.sampling.IndexSamplingConfig;
-import org.neo4j.kernel.impl.api.scan.LabelScanStoreProvider;
 import org.neo4j.kernel.impl.storemigration.StoreMigrationParticipant;
 import org.neo4j.kernel.lifecycle.LifecycleAdapter;
 
@@ -121,7 +120,7 @@ public InternalIndexState getInitialState( long indexId, IndexDescriptor descrip
 
                 @Override
                 public StoreMigrationParticipant storeMigrationParticipant( FileSystemAbstraction fs,
-                        PageCache pageCache, LabelScanStoreProvider labelScanStoreProvider )
+                        PageCache pageCache )
                 {
                     return StoreMigrationParticipant.NOT_PARTICIPATING;
                 }
@@ -220,8 +219,7 @@ public File getSchemaIndexStoreDirectory( File storeDir )
         return new File( new File( new File( storeDir, "schema" ), "index" ), getProviderDescriptor().getKey() );
     }
 
-    public abstract StoreMigrationParticipant storeMigrationParticipant( FileSystemAbstraction fs, PageCache pageCache,
-            LabelScanStoreProvider labelScanStoreProvider );
+    public abstract StoreMigrationParticipant storeMigrationParticipant( FileSystemAbstraction fs, PageCache pageCache );
 
     /**
      * Provides a snapshot of meta files about this index provider, not the indexes themselves.

community/kernel/src/main/java/org/neo4j/kernel/impl/api/scan/FullLabelStream.java

@@ -22,7 +22,6 @@
 import org.apache.commons.lang3.ArrayUtils;
 
 import java.io.IOException;
-import java.util.function.Supplier;
 
 import org.neo4j.helpers.collection.Visitor;
 import org.neo4j.kernel.api.labelscan.LabelScanWriter;
@@ -37,22 +36,21 @@
  */
 public class FullLabelStream implements FullStoreChangeStream, Visitor<NodeLabelUpdate,IOException>
 {
-    private final Supplier<IndexStoreView> lazyIndexStoreView;
+    private final IndexStoreView indexStoreView;
     private LabelScanWriter writer;
     private long count;
 
-    public FullLabelStream( Supplier<IndexStoreView> lazyIndexStoreView )
+    public FullLabelStream( IndexStoreView indexStoreView )
     {
-        this.lazyIndexStoreView = lazyIndexStoreView;
+        this.indexStoreView = indexStoreView;
     }
 
     @Override
     public long applyTo( LabelScanWriter writer ) throws IOException
     {
         // Keep the write for using it in visit
         this.writer = writer;
-        IndexStoreView view = lazyIndexStoreView.get();
-        StoreScan<IOException> scan = view.visitNodes( ArrayUtils.EMPTY_INT_ARRAY, ALWAYS_TRUE_INT, null, this, true );
+        StoreScan<IOException> scan = indexStoreView.visitNodes( ArrayUtils.EMPTY_INT_ARRAY, ALWAYS_TRUE_INT, null, this, true );
         scan.run();
         return count;
     }