00001 /* 00002 * DistinctValues.hpp 00003 * 00004 * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved. 00005 * 00006 * Oracle is a registered trademarks of Oracle Corporation and/or its 00007 * affiliates. 00008 * 00009 * This software is the confidential and proprietary information of Oracle 00010 * Corporation. You shall not disclose such confidential and proprietary 00011 * information and shall use it only in accordance with the terms of the 00012 * license agreement you entered into with Oracle. 00013 * 00014 * This notice may not be removed or altered. 00015 */ 00016 #ifndef COH_DISTINCT_VALUES_HPP 00017 #define COH_DISTINCT_VALUES_HPP 00018 00019 #include "coherence/lang.ns" 00020 00021 #include "coherence/util/aggregator/AbstractAggregator.hpp" 00022 #include "coherence/util/ValueExtractor.hpp" 00023 00024 COH_OPEN_NAMESPACE3(coherence,util,aggregator) 00025 00026 00027 /** 00028 * Return the set of unique values extracted from a set of entries in a Map. 00029 * If the set of entries is empty, an empty set is returned. 00030 * 00031 * This aggregator could be used in combination with 00032 * coherence::util::extractor::MultiExtractor allowing 00033 * to collect all unique combinations (tuples) of a given set of attributes. 00034 * 00035 * The DistinctValues aggregator covers a simple case of a more generic 00036 * aggregation pattern implemented by the GroupAggregator, which in 00037 * addition to collecting all distinct values or tuples, runs an aggregation 00038 * against each distinct entry set (group). 00039 * 00040 * @author djl 2008.05.12 00041 */ 00042 class COH_EXPORT DistinctValues 00043 : public class_spec<DistinctValues, 00044 extends<AbstractAggregator> > 00045 { 00046 friend class factory<DistinctValues>; 00047 00048 // ----- constructors --------------------------------------------------- 00049 00050 protected: 00051 /** 00052 * Default constructor (necessary for the PortableObject interface). 00053 */ 00054 DistinctValues(); 00055 00056 /** 00057 * Construct a DistinceValues aggregator. 00058 * 00059 * @param vExtractor the extractor that provides a value in the form 00060 * of any object 00061 */ 00062 DistinctValues(ValueExtractor::View vExtractor); 00063 00064 00065 // ----- AbstractAggregator Interface ---------------------------------- 00066 00067 protected: 00068 /** 00069 * {@inheritDoc} 00070 */ 00071 virtual void init(bool fFinal); 00072 00073 /** 00074 * {@inheritDoc} 00075 */ 00076 virtual void process(Object::View vO, bool fFinal); 00077 00078 /** 00079 * {@inheritDoc} 00080 */ 00081 virtual Object::Holder finalizeResult(bool fFinal); 00082 00083 00084 // ----- internal helpers ----------------------------------------------- 00085 00086 protected: 00087 /** 00088 * Return a set that can be used to store distinct values, creating it 00089 * if one has not already been created. 00090 * 00091 * @return a set that can be used to store distinct values 00092 */ 00093 virtual Set::Handle ensureSet(); 00094 00095 00096 // ----- data members --------------------------------------------------- 00097 00098 protected: 00099 /** 00100 * The resulting set of distinct values. 00101 */ 00102 MemberHandle<Set> m_hSet; 00103 }; 00104 00105 COH_CLOSE_NAMESPACE3 00106 00107 #endif // COH_DISTINCT_VALUES_HPP