Oracle® Fusion Middleware C++ API Reference for Oracle Coherence: LessFilter Class Reference

Detailed Description

Filter

In a case when either result of a method invocation or a value to compare are equal to NULL, the evaluate test yields false. This approach is equivalent to the way the NULL values are handled by SQL.

Author:

djl 2008.03.06

Public Types

typedef spec::Handle

Handle

LessFilter Handle definition.

typedef spec::View

View

LessFilter View definition.

typedef spec::Holder

Holder

LessFilter Holder definition.

Public Member Functions

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

Protected Member Functions

LessFilter ()

Default constructor (necessary for the PortableObject interface).

LessFilter (ValueExtractor::View vValueExtractor, Comparable::View vComparable)

Construct a LessFilter for testing "Less" condition.

virtual bool

evaluateExtracted (Object::View vExtracted) const

Evaluate the specified extracted value.

Parameters:

vExtracted

an extracted value to evaluate

Constructor & Destructor Documentation

LessFilter	(	ValueExtractor::View	vValueExtractor,
		Comparable::View	vComparable
	)			`[protected]`

Construct a LessFilter for testing "Less" condition.

Parameters:

	vValueExtractor	the ValueExtractor to use by this filter
	vComparable	the object to compare the result with

coherence/util/filter/LessFilter.hpp