Package com.tangosol.util.filter

Class PresentFilter<T>

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.filter.PresentFilter<T>
Type Parameters:
T - the type of the input argument to the filter
All Implemented Interfaces:
ExternalizableLite, PortableObject, Filter<T>, EntryFilter<Object,T>, IndexAwareFilter<Object,T>, Serializable
public class PresentFilter<T> extends ExternalizableHelper implements Filter<T>, EntryFilter<Object,T>, IndexAwareFilter<Object,T>, ExternalizableLite, PortableObject
Filter which returns true for InvocableMap.Entry objects that currently exist in a Map.

This Filter is intended to be used solely in combination with a ConditionalProcessor and is unnecessary for standard QueryMap operations.

Author:
jh 2005.12.16
See Also:

  • Field Details

    • INSTANCE

      public static final PresentFilter INSTANCE
      An instance of the PresentFilter.

  • Constructor Details

    • PresentFilter

      public PresentFilter()
      Construct a PresentFilter.

  • Method Details

    • 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

    • equals

      public boolean equals(Object o)
      Compare the PresentFilter with another object to determine equality.
      Overrides:
      equals in class Object
      Returns:
      true iff this PresentFilter and the passed object are equivalent PresentFilters

    • hashCode

      public int hashCode()
      Determine a hash value for the PresentFilter object according to the general Object.hashCode() contract.
      Overrides:
      hashCode in class Object
      Returns:
      an integer hash value for this PresentFilter object

    • 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(DataInput in) throws IOException
      Restore the contents of this object by loading the object's state from the passed DataInput object.
      Specified by:
      readExternal in interface ExternalizableLite
      Parameters:
      in - the DataInput stream to read data from in order to restore the state of this object
      Throws:
      IOException - if an I/O exception occurs

    • writeExternal

      public void writeExternal(DataOutput out) throws IOException
      Save the contents of this object by storing the object's state into the passed DataOutput object.
      Specified by:
      writeExternal in interface ExternalizableLite
      Parameters:
      out - the DataOutput stream to write the state of this object to
      Throws:
      IOException - if an I/O exception occurs

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

    • INSTANCE

      public static <T> PresentFilter<T> INSTANCE()
      Return an instance of the PresentFilter.
      Type Parameters:
      T - the type of the input argument to the filter
      Returns:
      a PresentFilter instance