00001 /* 00002 * Copyright (c) 2000, 2020, Oracle and/or its affiliates. 00003 * 00004 * Licensed under the Universal Permissive License v 1.0 as shown at 00005 * http://oss.oracle.com/licenses/upl. 00006 */ 00007 #ifndef COH_DISTINCT_VALUES_HPP 00008 #define COH_DISTINCT_VALUES_HPP 00009 00010 #include "coherence/lang.ns" 00011 00012 #include "coherence/util/aggregator/AbstractAggregator.hpp" 00013 #include "coherence/util/ValueExtractor.hpp" 00014 00015 COH_OPEN_NAMESPACE3(coherence,util,aggregator) 00016 00017 00018 /** 00019 * Return the set of unique values extracted from a set of entries in a Map. 00020 * If the set of entries is empty, an empty set is returned. 00021 * 00022 * This aggregator could be used in combination with 00023 * coherence::util::extractor::MultiExtractor allowing 00024 * to collect all unique combinations (tuples) of a given set of attributes. 00025 * 00026 * The DistinctValues aggregator covers a simple case of a more generic 00027 * aggregation pattern implemented by the GroupAggregator, which in 00028 * addition to collecting all distinct values or tuples, runs an aggregation 00029 * against each distinct entry set (group). 00030 * 00031 * @author djl 2008.05.12 00032 */ 00033 class COH_EXPORT DistinctValues 00034 : public class_spec<DistinctValues, 00035 extends<AbstractAggregator> > 00036 { 00037 friend class factory<DistinctValues>; 00038 00039 // ----- constructors --------------------------------------------------- 00040 00041 protected: 00042 /** 00043 * Default constructor (necessary for the PortableObject interface). 00044 */ 00045 DistinctValues(); 00046 00047 /** 00048 * Construct a DistinceValues aggregator. 00049 * 00050 * @param vExtractor the extractor that provides a value in the form 00051 * of any object 00052 */ 00053 DistinctValues(ValueExtractor::View vExtractor); 00054 00055 00056 // ----- AbstractAggregator Interface ---------------------------------- 00057 00058 protected: 00059 /** 00060 * {@inheritDoc} 00061 */ 00062 virtual void init(bool fFinal); 00063 00064 /** 00065 * {@inheritDoc} 00066 */ 00067 virtual void process(Object::View vO, bool fFinal); 00068 00069 /** 00070 * {@inheritDoc} 00071 */ 00072 virtual Object::Holder finalizeResult(bool fFinal); 00073 00074 00075 // ----- internal helpers ----------------------------------------------- 00076 00077 protected: 00078 /** 00079 * Return a set that can be used to store distinct values, creating it 00080 * if one has not already been created. 00081 * 00082 * @return a set that can be used to store distinct values 00083 */ 00084 virtual Set::Handle ensureSet(); 00085 00086 00087 // ----- data members --------------------------------------------------- 00088 00089 protected: 00090 /** 00091 * The resulting set of distinct values. 00092 */ 00093 MemberHandle<Set> m_hSet; 00094 }; 00095 00096 COH_CLOSE_NAMESPACE3 00097 00098 #endif // COH_DISTINCT_VALUES_HPP