Xapian::Weight Class Reference

Abstract base class for weighting schemes. More...

#include <enquire.h>

Inheritance diagram for Xapian::Weight:

[legend]List of all members.

Public Member Functions
Weight *	create (const Internal *internal_, Xapian::doclength querysize_, Xapian::termcount wqf_, const std::string &tname_) const
	Create a new weight object of the same type as this and initialise it with the specified statistics.
virtual std::string	name () const=0
	Name of the weighting scheme.
virtual std::string	serialise () const=0
	Serialise object parameters into a string.
virtual Weight *	unserialise (const std::string &s) const=0
	Create object given string serialisation returned by serialise().
virtual Xapian::weight	get_sumpart (Xapian::termcount wdf, Xapian::doclength len) const=0
	Get a weight which is part of the sum over terms being performed.
virtual Xapian::weight	get_maxpart () const=0
	Gets the maximum value that get_sumpart() may return.
virtual Xapian::weight	get_sumextra (Xapian::doclength len) const=0
	Get an extra weight for a document to add to the sum calculated over the query terms.
virtual Xapian::weight	get_maxextra () const=0
	Gets the maximum value that get_sumextra() may return.
virtual bool	get_sumpart_needs_doclength () const
	return false if the weight object doesn't need doclength
Protected Member Functions
	Weight (const Weight &)
Protected Attributes
const Internal *	internal
Xapian::doclength	querysize
Xapian::termcount	wqf
std::string	tname
Friends
class	Enquire
class	::RemoteServer
class	::ScaleWeight

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Detailed Description

Abstract base class for weighting schemes.

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Member Function Documentation

Weight* Xapian::Weight::create	(	const Internal *	internal_,
		Xapian::doclength	querysize_,
		Xapian::termcount	wqf_,
		const std::string &	tname_
	)			const

Create a new weight object of the same type as this and initialise it with the specified statistics.

You shouldn't call this method yourself - it's called by Enquire.

Parameters:

	internal_	Object to ask for collection statistics.
	querysize_	Query size.
	wqf_	Within query frequency of term this object is associated with.
	tname_	Term which this object is associated with.

virtual std::string Xapian::Weight::name

(

)

const [pure virtual]

Name of the weighting scheme.

If the subclass is called FooWeight, this should return "Foo".

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual std::string Xapian::Weight::serialise

(

)

const [pure virtual]

Serialise object parameters into a string.

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual Weight* Xapian::Weight::unserialise

(

const std::string &

s

)

const [pure virtual]

Create object given string serialisation returned by serialise().

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual Xapian::weight Xapian::Weight::get_sumpart	(	Xapian::termcount	wdf,
		Xapian::doclength	len
	)			const [pure virtual]

Get a weight which is part of the sum over terms being performed.

This returns a weight for a given term and document. These weights are summed to give a total weight for the document.

Parameters:

	wdf	the within document frequency of the term.
	len	the (unnormalised) document length.

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual Xapian::weight Xapian::Weight::get_maxpart

(

)

const [pure virtual]

Gets the maximum value that get_sumpart() may return.

This is used in optimising searches, by having the postlist tree decay appropriately when parts of it can have limited, or no, further effect.

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual Xapian::weight Xapian::Weight::get_sumextra

(

Xapian::doclength

len

)

const [pure virtual]

Get an extra weight for a document to add to the sum calculated over the query terms.

This returns a weight for a given document, and is used by some weighting schemes to account for influence such as document length.

Parameters:

len

the (unnormalised) document length.

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual Xapian::weight Xapian::Weight::get_maxextra

(

)

const [pure virtual]

Gets the maximum value that get_sumextra() may return.

This is used in optimising searches.

Implemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

virtual bool Xapian::Weight::get_sumpart_needs_doclength

(

)

const [virtual]

return false if the weight object doesn't need doclength

Reimplemented in Xapian::BoolWeight, Xapian::BM25Weight, and Xapian::TradWeight.

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

• include/xapian/enquire.h

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