Xapian::Weight subclass which adds laziness. More...

Inheritance diagram for LazyWeight:

Collaboration diagram for LazyWeight:

Public Member Functions
	LazyWeight (LeafPostList pl_, Xapian::Weight real_wt_, Xapian::Weight::Internal stats_, Xapian::termcount qlen_, Xapian::termcount wqf__, double factor_, const Xapian::Database::Internal shard_)

std::string	name () const override
	Return the name of this weighting scheme, e.g. More...

std::string	serialise () const override
	Return this object's parameters serialised as a single string. More...

LazyWeight *	unserialise (const std::string &serialised) const override
	Unserialise parameters. More...

double	get_sumpart (Xapian::termcount wdf, Xapian::termcount doclen, Xapian::termcount uniqterms, Xapian::termcount wdfdocmax) const override
	Calculate the weight contribution for this object's term to a document. More...

double	get_maxpart () const override
	Return an upper bound on what get_sumpart() can return for any document. More...

double	get_sumextra (Xapian::termcount doclen, Xapian::termcount uniqterms, Xapian::termcount wdfdocmax) const override
	Calculate the term-independent weight component for a document. More...

double	get_maxextra () const override
	Return an upper bound on what get_sumextra() can return for any document. More...

Public Member Functions inherited from Xapian::Weight
	Weight ()
	Default constructor, needed by subclass constructors. More...

virtual	~Weight ()
	Virtual destructor, because we have virtual methods. More...

virtual Weight *	create_from_parameters (const char *params) const
	Create from a human-readable parameter string. More...

Private Member Functions
LazyWeight *	clone () const override
	Clone this object. More...

void	init (double factor_) override
	Allow the subclass to perform any initialisation it needs to. More...

Private Attributes
LeafPostList *	pl

Xapian::Weight *	real_wt

Xapian::Weight::Internal *	stats

Xapian::termcount	qlen

Xapian::termcount	wqf

double	factor

const Xapian::Database::Internal *	shard

Additional Inherited Members
Static Public Member Functions inherited from Xapian::Weight
static const Weight *	create (const std::string &scheme, const Registry &reg=Registry())
	Return the appropriate weighting scheme object. More...

Protected Types inherited from Xapian::Weight
enum	stat_flags { COLLECTION_SIZE = 0 , RSET_SIZE = 0 , AVERAGE_LENGTH = 4 , TERMFREQ = 1 , RELTERMFREQ = 1 , QUERY_LENGTH = 0 , WQF = 0 , WDF = 2 , DOC_LENGTH = 8 , DOC_LENGTH_MIN = 16 , DOC_LENGTH_MAX = 32 , WDF_MAX = 64 , COLLECTION_FREQ = 1 , UNIQUE_TERMS = 128 , TOTAL_LENGTH = 256 , WDF_DOC_MAX = 512 , UNIQUE_TERMS_MIN = 1024 , UNIQUE_TERMS_MAX = 2048 , DB_DOC_LENGTH_MIN = 4096 , DB_DOC_LENGTH_MAX = 8192 , DB_UNIQUE_TERMS_MIN = 16384 , DB_UNIQUE_TERMS_MAX = 32768 , DB_WDF_MAX = 65536 , IS_BOOLWEIGHT_ = static_cast<int>(0x80000000) }
	Stats which the weighting scheme can use (see need_stat()). More...

Protected Member Functions inherited from Xapian::Weight
void	need_stat (stat_flags flag)
	Tell Xapian that your subclass will want a particular statistic. More...

	Weight (const Weight &)
	Don't allow copying. More...

Xapian::doccount	get_collection_size () const
	The number of documents in the collection. More...

Xapian::doccount	get_rset_size () const
	The number of documents marked as relevant. More...

Xapian::doclength	get_average_length () const
	The average length of a document in the collection. More...

Xapian::doccount	get_termfreq () const
	The number of documents which this term indexes. More...

Xapian::doccount	get_reltermfreq () const
	The number of relevant documents which this term indexes. More...

Xapian::termcount	get_collection_freq () const
	The collection frequency of the term. More...

Xapian::termcount	get_query_length () const
	The length of the query. More...

Xapian::termcount	get_wqf () const
	The within-query-frequency of this term. More...

Xapian::termcount	get_doclength_upper_bound () const
	An upper bound on the maximum length of any document in the shard. More...

Xapian::termcount	get_doclength_lower_bound () const
	A lower bound on the minimum length of any document in the shard. More...

Xapian::termcount	get_wdf_upper_bound () const
	An upper bound on the wdf of this term in the shard. More...

Xapian::totallength	get_total_length () const
	Total length of all documents in the collection. More...

Xapian::termcount	get_unique_terms_upper_bound () const
	A lower bound on the number of unique terms in any document in the shard. More...

Xapian::termcount	get_unique_terms_lower_bound () const
	An upper bound on the number of unique terms in any document in the shard. More...

Xapian::termcount	get_db_doclength_upper_bound () const
	An upper bound on the maximum length of any document in the database. More...

Xapian::termcount	get_db_doclength_lower_bound () const
	A lower bound on the minimum length of any document in the database. More...

Xapian::termcount	get_db_unique_terms_upper_bound () const
	A lower bound on the number of unique terms in any document in the database. More...

Xapian::termcount	get_db_unique_terms_lower_bound () const
	An upper bound on the number of unique terms in any document in the database. More...

Xapian::termcount	get_db_wdf_upper_bound () const
	An upper bound on the wdf of this term in the database. More...

Detailed Description

Xapian::Weight subclass which adds laziness.

For terms from a wildcard when remote databases are involved, we need to delay calling init_() on the weight object until the stats for the terms from the wildcard have been collated.

Definition at line 49 of file localsubmatch.cc.

Constructor & Destructor Documentation

◆ LazyWeight()

LazyWeight::LazyWeight	(	LeafPostList *	pl_,
		Xapian::Weight *	real_wt_,
		Xapian::Weight::Internal *	stats_,
		Xapian::termcount	qlen_,
		Xapian::termcount	wqf__,
		double	factor_,
		const Xapian::Database::Internal *	shard_
	)

inline

Definition at line 69 of file localsubmatch.cc.

Member Function Documentation

◆ clone()

LazyWeight * LazyWeight::clone ( ) const

overrideprivatevirtual

Clone this object.

This method allocates and returns a copy of the object it is called on.

If your subclass is called FooWeight and has parameters a and b, then you would implement FooWeight::clone() like so:

FooWeight * FooWeight::clone() const { return new FooWeight(a, b); }

Note that the returned object will be deallocated by Xapian after use with "delete". If you want to handle the deletion in a special way (for example when wrapping the Xapian API for use from another language) then you can define a static operator delete method in your subclass as shown here: https://trac.xapian.org/ticket/554#comment:1

Implements Xapian::Weight.

Definition at line 103 of file localsubmatch.cc.

◆ get_maxextra()

double LazyWeight::get_maxextra ( ) const

overridevirtual

Return an upper bound on what get_sumextra() can return for any document.

The default implementation always returns 0 (in Xapian < 2.0.0 this was a pure virtual method).

This information is used by the matcher to perform various optimisations, so strive to make the bound as tight as possible.

Reimplemented from Xapian::Weight.

Definition at line 168 of file localsubmatch.cc.

◆ get_maxpart()

double LazyWeight::get_maxpart ( ) const

overridevirtual

Return an upper bound on what get_sumpart() can return for any document.

This information is used by the matcher to perform various optimisations, so strive to make the bound as tight as possible.

Implements Xapian::Weight.

Definition at line 161 of file localsubmatch.cc.

◆ get_sumextra()

double LazyWeight::get_sumextra	(	Xapian::termcount	doclen,
		Xapian::termcount	uniqterms,
		Xapian::termcount	wdfdocmax
	)		const

overridevirtual

Calculate the term-independent weight component for a document.

The default implementation always returns 0 (in Xapian < 2.0.0 this was a pure virtual method).

The parameter gives information about the document which may be used in the calculations:

Parameters

doclen	The document's length (unnormalised). You need to call need_stat(DOC_LENGTH) if you use this value.
uniqterms	Number of unique terms in the document. You need to call need_stat(UNIQUE_TERMS) if you use this value.
wdfdocmax	Maximum wdf value in the document. You need to call need_stat(WDF_DOC_MAX) if you use this value.

Since: The wdfdocmax parameter was added in Xapian 2.0.0.

Reimplemented from Xapian::Weight.

Definition at line 150 of file localsubmatch.cc.

◆ get_sumpart()

double LazyWeight::get_sumpart	(	Xapian::termcount	wdf,
		Xapian::termcount	doclen,
		Xapian::termcount	uniqterms,
		Xapian::termcount	wdfdocmax
	)		const

overridevirtual

Calculate the weight contribution for this object's term to a document.

The parameters give information about the document which may be used in the calculations:

Parameters

wdf	The within document frequency of the term in the document. You need to call need_stat(WDF) if you use this value.
doclen	The document's length (unnormalised). You need to call need_stat(DOC_LENGTH) if you use this value.
uniqterms	Number of unique terms in the document. You need to call need_stat(UNIQUE_TERMS) if you use this value.
wdfdocmax	Maximum wdf value in the document. You need to call need_stat(WDF_DOC_MAX) if you use this value.

You can rely of wdf <= doclen if you call both need_stat(WDF) and need_stat(DOC_LENGTH) - this is trivially true for terms, but Xapian also ensure it's true for OP_SYNONYM, where the wdf is approximated.

Since: The wdfdocmax parameter was added in Xapian 2.0.0.

Implements Xapian::Weight.

Definition at line 137 of file localsubmatch.cc.

◆ init()

void LazyWeight::init ( double factor )

overrideprivatevirtual

Allow the subclass to perform any initialisation it needs to.

Parameters

factor Any scaling factor (e.g. from OP_SCALE_WEIGHT). If the Weight object is for the term-independent weight supplied by get_sumextra()/get_maxextra(), then init(0.0) is called (starting from Xapian 1.2.11 and 1.3.1 - earlier versions failed to call init() for such Weight objects).

Implements Xapian::Weight.

Definition at line 109 of file localsubmatch.cc.

◆ name()

string LazyWeight::name ( ) const

overridevirtual

Return the name of this weighting scheme, e.g.

"bm25+".

This is the name that the weighting scheme gets registered under when passed to Xapian:Registry::register_weighting_scheme().

As a result:

this is the name that needs to be used in Weight::create() to create a Weight object from a human-readable string description.
it is also used by the remote backend where it is sent (along with the serialised parameters) to the remote server so that it knows which class to create.

For 1.4.x and earlier we recommended returning the full namespace-qualified name of your class here, but now we recommend returning a just the name in lower case, e.g. "foo" instead of "FooWeight", "bm25+" instead of "Xapian::BM25PlusWeight".

If you don't want to support creation via Weight::create() or the remote backend, you can use the default implementation which simply returns an empty string.

Reimplemented from Xapian::Weight.

Definition at line 116 of file localsubmatch.cc.

◆ serialise()

string LazyWeight::serialise ( ) const

overridevirtual

Return this object's parameters serialised as a single string.

If you don't want to support the remote backend, you can use the default implementation which simply throws Xapian::UnimplementedError.

Reimplemented from Xapian::Weight.

Definition at line 125 of file localsubmatch.cc.

◆ unserialise()

LazyWeight * LazyWeight::unserialise ( const std::string & serialised ) const

overridevirtual

Unserialise parameters.

This method unserialises parameters serialised by the serialise() method and allocates and returns a new object initialised with them.

If you don't want to support the remote backend, you can use the default implementation which simply throws Xapian::UnimplementedError.

Note that the returned object will be deallocated by Xapian after use with "delete". If you want to handle the deletion in a special way (for example when wrapping the Xapian API for use from another language) then you can define a static operator delete method in your subclass as shown here: https://trac.xapian.org/ticket/554#comment:1

Parameters

serialised A string containing the serialised parameters.

Reimplemented from Xapian::Weight.

Definition at line 131 of file localsubmatch.cc.

Member Data Documentation

◆ factor

double LazyWeight::factor

private

Definition at line 60 of file localsubmatch.cc.

◆ pl

LeafPostList* LazyWeight::pl

private

Definition at line 50 of file localsubmatch.cc.

◆ qlen

Xapian::termcount LazyWeight::qlen

private

Definition at line 56 of file localsubmatch.cc.

◆ real_wt

Xapian::Weight* LazyWeight::real_wt

private

Definition at line 52 of file localsubmatch.cc.

◆ shard

const Xapian::Database::Internal* LazyWeight::shard

private

Definition at line 62 of file localsubmatch.cc.

◆ stats

Xapian::Weight::Internal* LazyWeight::stats

private

Definition at line 54 of file localsubmatch.cc.

◆ wqf

Xapian::termcount LazyWeight::wqf

private

Definition at line 58 of file localsubmatch.cc.

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

matcher/localsubmatch.cc

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ LazyWeight()

Member Function Documentation

◆ clone()

◆ get_maxextra()

◆ get_maxpart()

◆ get_sumextra()

◆ get_sumpart()

◆ init()

◆ name()

◆ serialise()

◆ unserialise()

Member Data Documentation

◆ factor

◆ pl

◆ qlen

◆ real_wt

◆ shard

◆ stats

◆ wqf