Oracle Coherence for C++ API: PriorityFilter Class Reference

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:

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.