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ReadGroupsFromCacheStep.java
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ReadGroupsFromCacheStep.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.unsafe.impl.batchimport;
import java.util.Arrays;
import java.util.Iterator;
import org.neo4j.helpers.collection.PrefetchingIterator;
import org.neo4j.kernel.impl.store.record.RelationshipGroupRecord;
import org.neo4j.unsafe.impl.batchimport.staging.PullingProducerStep;
import org.neo4j.unsafe.impl.batchimport.staging.StageControl;
import static org.neo4j.helpers.collection.Iterators.prefetching;
/**
* Reads {@link RelationshipGroupRecord group records} from {@link RelationshipGroupCache}, sending
* them downstream in batches.
*/
public class ReadGroupsFromCacheStep extends PullingProducerStep
{
private final int itemSize;
private final PrefetchingIterator<RelationshipGroupRecord> data;
private RelationshipGroupRecord[] scratch;
private int cursor;
public ReadGroupsFromCacheStep( StageControl control, Configuration config,
Iterator<RelationshipGroupRecord> groups, int itemSize )
{
super( control, config );
this.data = prefetching( groups );
this.itemSize = itemSize;
this.scratch = new RelationshipGroupRecord[config.batchSize() * 2]; // grows on demand
}
@Override
protected Object nextBatchOrNull( long ticket, int batchSize )
{
if ( !data.hasNext() )
{
return null;
}
int i = 0;
long lastOwner = -1;
for ( ; data.hasNext(); i++ )
{
// Logic below makes it so that all groups for a specific node ends up in the same batch,
// which means that batches are slightly bigger (varying) than the requested size.
RelationshipGroupRecord item = data.peek();
if ( i == batchSize - 1 )
{
// Remember which owner this "last" group has...
lastOwner = item.getOwningNode();
}
else if ( i >= batchSize )
{
// ...and continue including groups in this batch until next owner comes
if ( item.getOwningNode() != lastOwner )
{
break;
}
}
if ( i >= scratch.length )
{
scratch = Arrays.copyOf( scratch, scratch.length * 2 );
}
scratch[i] = data.next(); // which is "item", but also advances the iterator
cursor++;
}
return Arrays.copyOf( scratch, i );
}
@Override
protected long position()
{
return cursor * itemSize;
}
}