Oracle® Fusion Middleware C++ API Reference for Oracle Coherence
12c (12.2.1.3.0)
E80355-01

LimitFilter Class Reference

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

Inherits Object, IndexAwareFilter, and PortableObject.

Detailed Description

Filter which truncates the results of another filter.

This filter is a mutable object that is modified by the query processor. Clients are supposed to hold a reference to this filter and repetitively pass it to query methods after setting a desired page context calling setPage, nextPage(), or previousPage.

Author:: djl 2008.04.14

Public Types

typedef spec::Handle Handle

LimitFilter Handle definition.

typedef spec::View View

LimitFilter View definition.

typedef spec::Holder Holder

LimitFilter 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 TypedHandle
< const String > toString () const

Output a human-readable description of this Object to the given stream.

virtual Filter::View getFilter () const

Obtain the Filter whose results are truncated by this filter.

virtual int32_t getPageSize () const

Obtain the page size (expressed as a number of entries per page).

virtual void setPageSize (int32_t cPageSize)

Set the page size (expressed as a number of entries per page).

virtual int32_t getPage () const

Obtain a current page number (zero-based).

virtual void setPage (int32_t nPage)

Set the page number (zero-based).

virtual Comparator::View getComparator () const

Obtain the Comparator used to partition the entry values into pages.

virtual void setComparator (Comparator::View vComparator) const

Set the Comparator used to partition the values into pages.

virtual Object::View getTopAnchor () const

Obtain the top anchor object, which is the last value object on a previous page.

virtual void setTopAnchor (Object::View vAnchor) const

Set the top anchor object.

virtual Object::View getBottomAnchor () const

Obtain the bottom anchor object, which is the last value object on the current page.

virtual void setBottomAnchor (Object::View vAnchor) const

Set the bottom anchor object.

virtual Object::View getCookie () const

Obtain the cookie object.

virtual void setCookie (Object::View vCookie) const

Set the cookie object.

virtual void nextPage ()

Switch to the next page.

virtual void previousPage ()

Switch to the previous page.

virtual
ObjectArray::Handle extractPage (ObjectArray::Handle haEntry) const

Extract a subset of the specified array to fit the filter's parameters (i.e.

virtual
ObjectArray::Handle extractPage (Iterator::Handle hIter) const

Extract a subset of the specified iterator to fit the filter's parameters (i.e.

Protected Member Functions

LimitFilter ()

Default constructor (necessary for the PortableObject interface).

LimitFilter (Filter::View vFilter, int32_t cPageSize)

Construct a LimitFilter filter.

LimitFilter (const LimitFilter &that)

Copy constructor.

Constructor & Destructor Documentation

LimitFilter	(	Filter::View	vFilter,
		int32_t	cPageSize
	)			`[protected]`

Construct a LimitFilter filter.

Parameters:

	vFilter	the filter whose results this Filter truncates
	cPageSize	the sie of the page

Member Function Documentation

virtual TypedHandle<const String> toString ( ) const [virtual]

Output a human-readable description of this Object to the given stream.

Parameters:

out

the stream used to output the description

Reimplemented from Object.

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

Obtain the Filter whose results are truncated by this filter.

Returns:: the filter whose results are truncated by this filter

virtual int32_t getPageSize ( ) const [virtual]

Obtain the page size (expressed as a number of entries per page).

Returns:: the page size

virtual void setPageSize ( int32_t cPageSize ) [virtual]

Set the page size (expressed as a number of entries per page).

Parameters:

cPageSize

the page size

virtual int32_t getPage ( ) const [virtual]

Obtain a current page number (zero-based).

Returns:: the page number

virtual void setPage ( int32_t nPage ) [virtual]

Set the page number (zero-based).

Setting the page number to zero will reset the filter's state.

Parameters:

nPage

the page number

virtual Comparator::View getComparator ( ) const [virtual]

Obtain the Comparator used to partition the entry values into pages.