| /*- |
| * 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.je; |
| |
| /** |
| * A tag interface used to mark a B-tree or duplicate comparator class as a |
| * partial comparator. |
| * |
| * Comparators are configured using |
| * {@link DatabaseConfig#setBtreeComparator(java.util.Comparator)} or |
| * {@link DatabaseConfig#setBtreeComparator(Class)}, and |
| * {@link DatabaseConfig#setDuplicateComparator(java.util.Comparator)} or |
| * {@link DatabaseConfig#setDuplicateComparator(Class)}. |
| * <p> |
| * As described in the javadoc for these methods, a partial comparator is a |
| * comparator that allows for the keys of a database to be updated, but only |
| * if the updates are not significant with respect to uniqueness and ordering. |
| * Also described is the fact that comparators must be used with great caution, |
| * since a badly behaved comparator can cause B-tree corruption. |
| * <p> |
| * Even greater caution is needed when using partial comparators, for several |
| * reasons. Partial comparators are normally used for performance reasons in |
| * certain situations, but the performance trade-offs are very subtle and |
| * difficult to understand. In addition, as of JE 6, this tag interface must |
| * be added to all partial comparator classes so that JE can correctly perform |
| * transaction aborts, while maintaining the last committed key or duplicate |
| * data values properly. In addition, for a database with duplicates |
| * configured, a partial comparator (implementing this tag interface) will |
| * disable optimizations in JE 6 that drastically reduce cleaner costs. |
| * <p> |
| * For these reasons, we do not recommend using partial comparators, although |
| * they are supported in order to avoid breaking applications that used them |
| * prior to JE 6. Whenever possible, please avoid using partial comparators. |
| */ |
| public interface PartialComparator { |
| } |
