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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.impl.index.schema;

import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.nio.file.Path;

import org.neo4j.common.TokenNameLookup;
import org.neo4j.index.internal.gbptree.GBPTree;
import org.neo4j.index.internal.gbptree.Layout;
import org.neo4j.index.internal.gbptree.MetadataMismatchException;
import org.neo4j.index.internal.gbptree.RecoveryCleanupWorkCollector;
import org.neo4j.internal.kernel.api.InternalIndexState;
import org.neo4j.internal.schema.IndexDescriptor;
import org.neo4j.internal.schema.IndexProviderDescriptor;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.memory.ByteBufferFactory;
import org.neo4j.io.pagecache.PageCache;
import org.neo4j.io.pagecache.context.CursorContext;
import org.neo4j.kernel.api.index.IndexAccessor;
import org.neo4j.kernel.api.index.IndexDirectoryStructure.Factory;
import org.neo4j.kernel.api.index.IndexPopulator;
import org.neo4j.kernel.api.index.IndexProvider;
import org.neo4j.kernel.api.index.MinimalIndexAccessor;
import org.neo4j.kernel.impl.api.index.IndexSamplingConfig;
import org.neo4j.memory.MemoryTracker;
import org.neo4j.storageengine.api.StorageEngineFactory;
import org.neo4j.storageengine.migration.SchemaIndexMigrator;
import org.neo4j.storageengine.migration.StoreMigrationParticipant;

import static org.apache.commons.lang3.StringUtils.defaultIfEmpty;

/**
 * Base class for native indexes on top of {@link GBPTree}.
 *
 * @param  type of {@link NativeIndexKey}
 * @param  type of {@link IndexLayout}
 */
abstract class NativeIndexProvider,LAYOUT extends IndexLayout>
        extends IndexProvider
{
    protected final DatabaseIndexContext databaseIndexContext;
    protected final RecoveryCleanupWorkCollector recoveryCleanupWorkCollector;
    private final Monitor monitor;

    protected NativeIndexProvider( DatabaseIndexContext databaseIndexContext, IndexProviderDescriptor descriptor,
            Factory directoryStructureFactory, RecoveryCleanupWorkCollector recoveryCleanupWorkCollector )
    {
        super( descriptor, directoryStructureFactory );
        this.databaseIndexContext = databaseIndexContext;
        this.recoveryCleanupWorkCollector = recoveryCleanupWorkCollector;
        this.monitor = databaseIndexContext.monitors.newMonitor( IndexProvider.Monitor.class, databaseIndexContext.monitorTag );
    }

    /**
     * Instantiates the {@link Layout} which is used in the index backing this native index provider.
     *
     * @param descriptor the {@link IndexDescriptor} for this index.
     * @param storeFile  index store file, since some layouts may depend on contents of the header. If {@code null} it means that nothing must be read from the
     *                   file before or while instantiating the layout.
     * @return the correct {@link Layout} for the index.
     */
    abstract LAYOUT layout( IndexDescriptor descriptor, Path storeFile );

    @Override
    public MinimalIndexAccessor getMinimalIndexAccessor( IndexDescriptor descriptor )
    {
        return new NativeMinimalIndexAccessor( descriptor, indexFiles( descriptor ), databaseIndexContext.readOnlyChecker );
    }

    @Override
    public IndexPopulator getPopulator( IndexDescriptor descriptor, IndexSamplingConfig samplingConfig, ByteBufferFactory bufferFactory,
            MemoryTracker memoryTracker, TokenNameLookup tokenNameLookup )
    {
        if ( databaseIndexContext.readOnlyChecker.isReadOnly() )
        {
            throw new UnsupportedOperationException( "Can't create populator for read only index" );
        }

        IndexFiles indexFiles = indexFiles( descriptor );
        return newIndexPopulator( indexFiles, layout( descriptor, null /*meaning don't read from this file since we're recreating it anyway*/ ), descriptor,
                bufferFactory, memoryTracker, tokenNameLookup );
    }

    protected abstract IndexPopulator newIndexPopulator( IndexFiles indexFiles, LAYOUT layout, IndexDescriptor descriptor,
            ByteBufferFactory bufferFactory, MemoryTracker memoryTracker, TokenNameLookup tokenNameLookup );

    @Override
    public IndexAccessor getOnlineAccessor( IndexDescriptor descriptor, IndexSamplingConfig samplingConfig, TokenNameLookup tokenNameLookup ) throws IOException
    {
        IndexFiles indexFiles = indexFiles( descriptor );
        return newIndexAccessor( indexFiles, layout( descriptor, indexFiles.getStoreFile() ), descriptor, tokenNameLookup );
    }

    protected abstract IndexAccessor newIndexAccessor( IndexFiles indexFiles, LAYOUT layout, IndexDescriptor descriptor, TokenNameLookup tokenNameLookup )
            throws IOException;

    @Override
    public String getPopulationFailure( IndexDescriptor descriptor, CursorContext cursorContext )
    {
        try
        {
            String failureMessage =
                    NativeIndexes.readFailureMessage( databaseIndexContext.pageCache, storeFile( descriptor ), databaseIndexContext.databaseName,
                            cursorContext );
            return defaultIfEmpty( failureMessage, StringUtils.EMPTY );
        }
        catch ( IOException e )
        {
            throw new RuntimeException( e );
        }
    }

    @Override
    public InternalIndexState getInitialState( IndexDescriptor descriptor, CursorContext cursorContext )
    {
        try
        {
            return NativeIndexes.readState( databaseIndexContext.pageCache, storeFile( descriptor ), databaseIndexContext.databaseName, cursorContext );
        }
        catch ( MetadataMismatchException | IOException e )
        {
            monitor.failedToOpenIndex( descriptor, "Requesting re-population.", e );
            return InternalIndexState.POPULATING;
        }
    }

    @Override
    public StoreMigrationParticipant storeMigrationParticipant( FileSystemAbstraction fs, PageCache pageCache, StorageEngineFactory storageEngineFactory )
    {
        return new SchemaIndexMigrator( getProviderDescriptor().name() + " indexes", fs, pageCache, directoryStructure(), storageEngineFactory, false );
    }

    private Path storeFile( IndexDescriptor descriptor )
    {
        IndexFiles indexFiles = indexFiles( descriptor );
        return indexFiles.getStoreFile();
    }

    private IndexFiles indexFiles( IndexDescriptor descriptor )
    {
        return new IndexFiles.Directory( databaseIndexContext.fileSystem, directoryStructure(), descriptor.getId() );
    }
}