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Berkeley DB Java Edition is a open source, transactional storage solution for Java applications. The Direct Persistence Layer (DPL) API is faster and easier to develop, deploy, and manage than serialized object files or ORM-based Java persistence solutions. The Collections API enhances the standard java.util.collections classes allowing them to be persisted to a local file system and accessed concurrently while protected by ACID transactions. Data is stored by serializing objects and managing class and instance data separately so as not to waste space. Berkeley DB Java Edition is the reliable drop-in solution for complex, fast, and scalable storage. Source for this release is in 'je-4.0.92-sources.jar', the Javadoc is located at 'http://download.oracle.com/berkeley-db/docs/je/4.0.92/'.

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/*-
 * Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle Berkeley
 * DB Java Edition made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle Berkeley DB Java Edition for a copy of the
 * license and additional information.
 */

package com.sleepycat.persist;

/**
 * This is package-private to hide it until we implemented unsorted access.
 *
 * Implemented to select keys to be returned by an unsorted {@code
 * ForwardCursor}.
 *
 * The reason for implementing a selector, rather than filtering the objects
 * returned by the {@link ForwardCursor}, is to improve performance when not
 * all keys are to be processed.  Keys are passed to this interface without
 * retrieving record data or locking, so it is less expensive to return false
 * from this method than to retrieve the object from the cursor.
 *
 * see EntityIndex#unsortedKeys
 * see EntityIndex#unsortedEntities
 *
 * @author Mark Hayes
 */
interface KeySelector {

    /**
     * Returns whether a given key should be returned via the cursor.
     *
     * This method should not assume that the given key is for a committed
     * record or not, nor should it assume that the key will be returned via
     * the cursor if this method returns true.  The record for this key will
     * not be locked until this method returns.  If, when the record is locked,
     * the record is found to be uncommitted or deleted, the key will not be
     * returned via the cursor.
     */
    boolean selectKey(K key);
}