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ValueMergers.java
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ValueMergers.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.index.internal.gbptree;
/**
* Common {@link ValueMerger} implementations.
*/
public class ValueMergers
{
private static final ValueMerger OVERWRITE = ( existingKey, newKey, existingValue, newValue ) -> newValue;
private static final ValueMerger KEEP_EXISTING = ( existingKey, newKey, existingValue, newValue ) -> null;
private ValueMergers()
{
}
/**
* @return {@link ValueMerger} which overwrites value for existing key when inserting.
* This merger guarantees unique keys in index.
*/
@SuppressWarnings( "unchecked" )
public static <KEY,VALUE> ValueMerger<KEY,VALUE> overwrite()
{
return OVERWRITE;
}
/**
* @return {@link ValueMerger} which keeps existing key/value otherwise adds new key/value pair.
* This merger guarantees unique keys in index.
*/
@SuppressWarnings( "unchecked" )
public static <KEY,VALUE> ValueMerger<KEY,VALUE> keepExisting()
{
return KEEP_EXISTING;
}
}