org.neo4j.kernel.impl.index.schema.NativeAllEntriesTokenScanReader Maven / Gradle / Ivy
Show all versions of neo4j-kernel Show documentation
/*
* 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
* Token index uses {@link GBPTree} for storage and it doesn't have means of aggregating
* results, so the approach this implementation is taking is to create one (lazy) seek cursor per token id
* and coordinate those simultaneously over the scan. Each {@link EntityTokenRange} returned is a view
* over all cursors at that same range, giving an aggregation of all tokens in that entity id range.
*/
class NativeAllEntriesTokenScanReader implements AllEntriesTokenScanReader
{
private final IntFunction> seekProvider;
private final List> cursors = new ArrayList<>();
private final int highestTokenId;
private final EntityType entityType;
NativeAllEntriesTokenScanReader( IntFunction> seekProvider,
int highestTokenId, EntityType entityType )
{
this.seekProvider = seekProvider;
this.highestTokenId = highestTokenId;
this.entityType = entityType;
}
@Override
public long maxCount()
{
return BoundedIterable.UNKNOWN_MAX_COUNT;
}
@Override
public Iterator iterator()
{
try
{
long lowestRange = Long.MAX_VALUE;
closeCursors();
for ( int tokenId = 0; tokenId <= highestTokenId; tokenId++ )
{
Seeker cursor = seekProvider.apply( tokenId );
// Bootstrap the cursor, which also provides a great opportunity to exclude if empty
if ( cursor.next() )
{
lowestRange = min( lowestRange, cursor.key().idRange );
cursors.add( cursor );
}
}
return new EntityTokenRangeIterator( lowestRange, entityType );
}
catch ( IOException e )
{
throw new RuntimeException( e );
}
}
private void closeCursors() throws IOException
{
for ( Seeker cursor : cursors )
{
cursor.close();
}
cursors.clear();
}
@Override
public void close() throws Exception
{
closeCursors();
}
/**
* The main iterator over {@link EntityTokenRange ranges}, aggregating all the cursors as it goes.
*/
private class EntityTokenRangeIterator extends PrefetchingIterator
{
private long currentRange;
private final EntityType entityType;
// entityId (relative to lowestRange) --> tokenId[]
private final MutableLongList[] tokensForEachEntity = new MutableLongList[RANGE_SIZE];
EntityTokenRangeIterator( long lowestRange, EntityType entityType )
{
this.currentRange = lowestRange;
this.entityType = entityType;
}
@Override
protected EntityTokenRange fetchNextOrNull()
{
if ( currentRange == Long.MAX_VALUE )
{
return null;
}
Arrays.fill( tokensForEachEntity, null );
long nextLowestRange = Long.MAX_VALUE;
try
{
// One "rangeSize" range at a time
for ( var iterator = cursors.iterator(); iterator.hasNext(); )
{
var cursor = iterator.next();
long idRange = cursor.key().idRange;
if ( idRange < currentRange )
{
// This should never happen because if the cursor has been exhausted and the iterator have moved on
// from the range it returned as its last hit, that cursor is removed from the collection
throw new IllegalStateException( "Accessing cursor that is out of range" );
}
else if ( idRange == currentRange )
{
long bits = cursor.value().bits;
long tokenId = cursor.key().tokenId;
EntityTokenRangeImpl.readBitmap( bits, tokenId, tokensForEachEntity );
// Advance cursor and look ahead to the next range
if ( cursor.next() )
{
nextLowestRange = min( nextLowestRange, cursor.key().idRange );
}
else
{
// remove exhausted cursor so we never try to read from it again
cursor.close();
iterator.remove();
}
}
else
{
// Excluded from this range
nextLowestRange = min( nextLowestRange, cursor.key().idRange );
}
}
EntityTokenRange range = new EntityTokenRangeImpl( currentRange, EntityTokenRangeImpl.convertState( tokensForEachEntity ), entityType );
currentRange = nextLowestRange;
return range;
}
catch ( IOException e )
{
throw new RuntimeException( e );
}
}
}
}