Oracle Coherence for C++ API
Release 3.6.0.0
E15728-01

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# coherence/util/aggregator/DistinctValues.hpp

    00001 /*
    00002 * DistinctValues.hpp
    00003 *
    00004 * Copyright (c) 2000, 2010, 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

Copyright © 2000, 2010, Oracle and/or its affiliates. All rights reserved.