Package com.tangosol.util.filter

Class PriorityFilter<T>

  • All Implemented Interfaces:
    ExternalizableLite, PortableObject, PriorityTask, Filter<T>, EntryFilter<Object,​T>, IndexAwareFilter<Object,​T>, Serializable
    public class PriorityFilter<T>
extends AbstractPriorityTask
implements Filter<T>, EntryFilter<Object,​T>, IndexAwareFilter<Object,​T>, ExternalizableLite, PortableObject
    PriorityFilter is used to explicitly control the scheduling priority and timeouts for execution of filter-based methods.

    For example, let's assume that there is a cache that belongs to a partitioned cache service configured with a request-timeout and task-timeout of 5 seconds. Also assume that we are willing to wait longer for a particular rarely executed parallel query that does not employ any indexes. Then we could override the default timeout values by using the PriorityFilter as follows: 

       EqualsFilter   filterStandard = new LikeFilter("getComments", "%fail%");
   PriorityFilter filterPriority = new PriorityFilter(filterStandard);
   filterPriority.setExecutionTimeoutMillis(PriorityTask.TIMEOUT_NONE);
   filterPriority.setRequestTimeoutMillis(PriorityTask.TIMEOUT_NONE);
   Set setEntries = cache.entrySet(filterPriority);

    This is an advanced feature which should be used judiciously.

    Since:
    Coherence 3.3
    Author:
    gg 2007.03.20
    See Also:
    Serialized Form

    • Constructor Detail

      • PriorityFilter

        public PriorityFilter()
        Default constructor (necessary for the ExternalizableLite interface).

      • PriorityFilter

        public PriorityFilter​(IndexAwareFilter filter)
        Construct a PriorityFilter.
        Parameters:
        filter - the filter wrapped by this PriorityFilter

    • Method Detail

      • evaluate

        public boolean evaluate​(T 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 well this filter can use the specified indexes to filter the specified keys. An operation that requires no more than a single access to the index content (i.e. Equals, NotEquals) has an effectiveness of one. Evaluation of a single entry is assumed to have an effectiveness that depends on the index implementation and is usually measured as a constant number of the single operations. This number is referred to as evaluation cost.

        If the effectiveness of a filter evaluates to a number larger than the keySet.size() * <evaluation cost> then a user could avoid using the index and iterate through the keySet calling evaluate rather then applyIndex.

        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

      • getFilter

        public IndexAwareFilter getFilter()
        Obtain the underlying filter.
        Returns:
        the filter wrapped by this PriorityFilter

      • toString

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

      • readExternal

        public void readExternal​(PofReader in)
                  throws IOException
        Restore the contents of a user type instance by reading its state using the specified PofReader object.

        The AbstractPriorityTask implementation reserves property indexes 0 - 9.

        This implementation reserves property index 10.

        Specified by:
        readExternal in interface PortableObject
        Overrides:
        readExternal in class AbstractPriorityTask
        Parameters:
        in - the PofReader from which to read the object's state
        Throws:
        IOException - if an I/O error occurs

      • writeExternal

        public void writeExternal​(PofWriter out)
                   throws IOException
        Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

        The AbstractPriorityTask implementation reserves property indexes 0 - 9.

        This implementation reserves property index 10.

        Specified by:
        writeExternal in interface PortableObject
        Overrides:
        writeExternal in class AbstractPriorityTask
        Parameters:
        out - the PofWriter to which to write the object's state
        Throws:
        IOException - if an I/O error occurs