Oracle Coherence for C++ API
Release 3.7.1.0

E22845-01

PriorityFilter Class Reference

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

Inherits AbstractPriorityTask, and IndexAwareFilter.

List of all members.


Detailed Description

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::Handle   hFilterStandard = LikeFilter::create("getComments", "%fail%");
   PriorityFilter::Handle hFilterPriority = PriorityFilter::create(hFilterStandard);
   hFilterPriority->setExecutionTimeoutMillis(PriorityTask::timeout_none);
   hFilterPriority->setRequestTimeoutMillis(PriorityTask::timeout_none);
   Set::View vSetEntries = hCache->entrySet(hFilterPriority);
 

This is an advanced feature which should be used judiciously.

Author:
djl 2008.03.02
 

Public Types

typedef spec::Handle Handle
 PriorityFilter Handle definition.
typedef spec::View View
 PriorityFilter View definition.
typedef spec::Holder Holder
 PriorityFilter 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 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
virtual
IndexAwareFilter::View 
getFilter () const
 Obtain the underlying filter.

Protected Member Functions

 PriorityFilter ()
 Default constructor (necessary for the PortableObject interface).
 PriorityFilter (IndexAwareFilter::View vFilter)
 Construct a PriorityFilter.

Protected Attributes

MemberView
< IndexAwareFilter
m_vFilter
 The wrapped filter.

Constructor & Destructor Documentation

PriorityFilter ( IndexAwareFilter::View  vFilter  )  [protected]

Construct a PriorityFilter.

Parameters:
 vFilter the filter wrapped by this PriorityFilter


Member Function Documentation

virtual IndexAwareFilter::View getFilter (  )  const [virtual]

Obtain the underlying filter.

Returns:
the filter wrapped by this PriorityFilter


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