Package com.tangosol.util.filter

Class KeyFilter<T>

  • All Implemented Interfaces:
    Filter<T>, EntryFilter<Object,​T>, IndexAwareFilter<Object,​T>, Serializable
    public class KeyFilter<T>
extends Base
implements Filter<T>, EntryFilter<Object,​T>, IndexAwareFilter<Object,​T>
    EntryFilter which checks whether an entry key belongs to a set.

    Note: this filter is not serializable and intended to be used only internally by other composite filters to reduce the remaining key set.

    As of Coherence 3.2, an equivalent functionality could be achieved using the InFilter as follows: 

       new InFilter(new KeyExtractor(IdentityExtractor.INSTANCE), setKeys);
    Author:
    cp/gg 2002.11.01
    See Also:
    Serialized Form

    • Field Detail

      • m_setKeys

        protected Set m_setKeys
        The keys that are evaluated to true by this filter.

    • Constructor Detail

      • KeyFilter

        public KeyFilter​(Set<T> setKeys)
        Construct a key filter.
        Parameters:
        setKeys - the keys that this filter will evaluate to true

    • Method Detail

      • evaluate

        public boolean evaluate​(Object o)
        Apply the test to the input argument.
        Specified by:
        evaluate in interface Filter<T>
        Parameters:
        o - the input argument to evaluate
        Returns:
        true if the input argument matches the filter, otherwise false

      • evaluateEntry

        public boolean evaluateEntry​(Map.Entry entry)
        Apply the test to a Map Entry.
        Specified by:
        evaluateEntry in interface EntryFilter<Object,​T>
        Parameters:
        entry - the Map Entry to evaluate; never null
        Returns:
        true if the test passes, false otherwise

      • calculateEffectiveness

        public int calculateEffectiveness​(Map mapIndexes,
                                  Set setKeys)
        Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

        The returned value is an effectiveness estimate of how many keys will remain in the set after the index is applied. If no keys will remain in the set after the index is applied, this method should return 0. If all the keys will remain in the set, implying that no entries would be filtered out based on this filter, this method should return setKeys.size(). Otherwise, it should return the value between 0 and setKeys.size(). If there is no index in the specified index map that can be used by this filter, this method should return a negative integer.

        The effectiveness returned will be used by the composite filters to reorder nested filters from most to least effective, in order to optimize query execution.

        Specified by:
        calculateEffectiveness in interface IndexAwareFilter<Object,​T>
        Parameters:
        mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
        setKeys - the set of keys that will be filtered; read-only
        Returns:
        an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys

      • applyIndex

        public Filter applyIndex​(Map mapIndexes,
                         Set setKeys)
        Filter remaining keys using a Map of available indexes.

        The filter is responsible for removing all keys from the passed set of keys that the applicable indexes can prove should be filtered. If the filter does not fully evaluate the remaining keys using just the index information, it must return a filter (which may be an EntryFilter) that can complete the task using an iterating implementation. If, on the other hand, the filter does fully evaluate the remaining keys using just the index information, then it should return null to indicate that no further filtering is necessary.

        Specified by:
        applyIndex in interface IndexAwareFilter<Object,​T>
        Parameters:
        mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
        setKeys - the mutable set of keys that remain to be filtered
        Returns:
        a Filter object (which may be an EntryFilter) that can be used to process the remaining keys, or null if no additional filter processing is necessary

      • getKeys

        public Set getKeys()
        Get the set of keys that are evaluated to true by this filter.
        Returns:
        the set of keys

      • toString

        public String toString()
        Return a human-readable description for this Filter.
        Overrides:
        toString in class Object
        Returns:
        a String description of the Filter