Oracle Coherence for C++ API
Release 3.6.0.0

E15728-01

PresentFilter Class Reference

#include <coherence/util/filter/PresentFilter.hpp>

Inherits Object, IndexAwareFilter, and PortableObject.

List of all members.


Detailed Description

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:
djl 2008.04.08

Public Types

typedef spec::Handle Handle
 PresentFilter Handle definition.
typedef spec::View View
 PresentFilter View definition.
typedef spec::Holder Holder
 PresentFilter Holder definition.

Public Member Functions

virtual bool evaluateEntry (Map::Entry::View vEntry) const
 Apply the test to a Map::Entry.

Parameters:
vEntry the Map::Entry to evaluate; never NULL
Returns:
true if the test passes, false otherwise

virtual bool evaluate (Object::View v) const
 Apply the test to the object.

Parameters:
v the object to test
Returns:
true if the test passes, false otherwise

virtual size32_t calculateEffectiveness (Map::View vMapIndexes, Set::View vSetKeys) const
 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.

Parameters:
vMapIndexes the available MapIndex objects keyed by the related ValueExtractor; read-only
vSetKeys 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

virtual Filter::View applyIndex (Map::View vMapIndexes, Set::Handle hSetKeys) const
 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.

Parameters:
vMapIndexes the available MapIndex objects keyed by the related ValueExtractor; read-only
hSetKeys 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

virtual void readExternal (PofReader::Handle hIn)
 
virtual void writeExternal (PofWriter::Handle hOut) const
 
virtual bool equals (Object::View v) const
 
virtual size32_t hashCode () const
 Return a hash code value for the Object.

This method is supported for the benefit of hash-based containers.

The general contract of hashCode is:

  • Whenever it is invoked on the same Object more than once during an execution of an application, the hashCode method must consistently return the same value, provided no information used in equals comparisons on the object is modified. This value need not remain consistent from one execution of an application to another execution of the same application.
  • If two Objects are equal according to the equals method, then calling the hashCode method on each of the two Objects must produce the same value.
  • It is not required that if two Objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct results. However, the programmer should be aware that producing distinct results for unequal objects may improve the performance of hash-based containers.

The default implementation is identity based.

Returns:
a hash code value for this Object

virtual void toStream (std::ostream &out) const
 Output a human-readable description of this Object to the given stream.

coherence::lang::operator<<(std::ostream, Object::View) is defined and will call into the toStream method, to output Objects. If a managed String object is desired, the COH_TO_STRING macro can be used to build up a String from streamable contents.

 Object::View vKey   = ...
 Object::View vValue = ...
 std::cout << vKey << " = " << vValue << std::endl;

 String::Handle hs = COH_TO_STRING(vKey << " = " << vValue);

Parameters:
out the stream used to output the description


Static Public Member Functions

static
PresentFilter::Handle 
getInstance ()
 An instance of the PresentFilter.

Protected Member Functions

 PresentFilter ()
 Construct a PresentFilter.

The documentation for this class was generated from the following file:
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