org.neo4j.kernel.impl.newapi.LockingNodeUniqueIndexSeek Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of neo4j-kernel Show documentation
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.
There is a newer version: 5.25.1
Show newest version
/*
 * 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.newapi;

import org.neo4j.internal.kernel.api.PropertyIndexQuery;
import org.neo4j.internal.kernel.api.NodeValueIndexCursor;
import org.neo4j.internal.kernel.api.exceptions.schema.IndexNotApplicableKernelException;
import org.neo4j.internal.kernel.api.exceptions.schema.IndexNotFoundKernelException;
import org.neo4j.internal.schema.IndexDescriptor;
import org.neo4j.kernel.api.StatementConstants;
import org.neo4j.kernel.api.index.IndexReader;
import org.neo4j.kernel.api.index.ValueIndexReader;
import org.neo4j.kernel.impl.locking.Locks;
import org.neo4j.lock.LockTracer;

import static org.neo4j.kernel.impl.locking.ResourceIds.indexEntryResourceId;
import static org.neo4j.lock.ResourceTypes.INDEX_ENTRY;

public class LockingNodeUniqueIndexSeek
{
    public static  long apply( Locks.Client locks,
                                                                    LockTracer lockTracer,
                                                                    CURSOR cursor,
                                                                    UniqueNodeIndexSeeker nodeIndexSeeker,
                                                                    Read read,
                                                                    IndexDescriptor index,
                                                                    PropertyIndexQuery.ExactPredicate... predicates )
            throws IndexNotApplicableKernelException, IndexNotFoundKernelException
    {
        int[] entityTokenIds = index.schema().getEntityTokenIds();
        if ( entityTokenIds.length != 1 )
        {
            throw new IndexNotApplicableKernelException( "Multi-token index " + index + " does not support uniqueness." );
        }
        long indexEntryId = indexEntryResourceId( entityTokenIds[0], predicates );

        //First try to find node under a shared lock
        //if not found upgrade to exclusive and try again
        locks.acquireShared( lockTracer, INDEX_ENTRY, indexEntryId );
        try ( IndexReaders readers = new IndexReaders( index, read ) )
        {
            nodeIndexSeeker.nodeIndexSeekWithFreshIndexReader( cursor, readers.createReader(), predicates );
            if ( !cursor.next() )
            {
                locks.releaseShared( INDEX_ENTRY, indexEntryId );
                locks.acquireExclusive( lockTracer, INDEX_ENTRY, indexEntryId );
                nodeIndexSeeker.nodeIndexSeekWithFreshIndexReader( cursor, readers.createReader(), predicates );
                if ( cursor.next() ) // we found it under the exclusive lock
                {
                    // downgrade to a shared lock
                    locks.acquireShared( lockTracer, INDEX_ENTRY, indexEntryId );
                    locks.releaseExclusive( INDEX_ENTRY, indexEntryId );
                    return cursor.nodeReference();
                }
                else
                {
                    return StatementConstants.NO_SUCH_NODE;
                }
            }

            return cursor.nodeReference();
        }
    }

    @FunctionalInterface
    interface UniqueNodeIndexSeeker
    {
        void nodeIndexSeekWithFreshIndexReader( CURSOR cursor,
                                                ValueIndexReader indexReader,
                                                PropertyIndexQuery.ExactPredicate... predicates ) throws IndexNotApplicableKernelException;
    }
}