XorPostList Class Reference

A postlist comprising two postlists XORed together. More...

#include <xorpostlist.h>

Inheritance diagram for XorPostList:

[legend]Collaboration diagram for XorPostList:


Public Member Functions
Xapian::doccount	get_termfreq_max () const
	Get an upper bound on the number of documents indexed by this term.
Xapian::doccount	get_termfreq_min () const
	Get a lower bound on the number of documents indexed by this term.
Xapian::doccount	get_termfreq_est () const
	Get an estimate of the number of documents indexed by this term.
Xapian::docid	get_docid () const
	Return the current docid.
Xapian::weight	get_weight () const
	Return the weight contribution for the current position.
Xapian::weight	get_maxweight () const
	Return an upper bound on what get_weight() can return.
Xapian::weight	recalc_maxweight ()
	Recalculate the upper bound on what get_weight() can return.
PostList *	next (Xapian::weight w_min)
	Advance the current position to the next document in the postlist.
PostList *	skip_to (Xapian::docid did, Xapian::weight w_min)
	Skip forward to the specified docid.
bool	at_end () const
	Return true if the current position is past the last entry in this list.
std::string	get_description () const
	Return a string description of this object.
virtual Xapian::doclength	get_doclength () const
	Return the document length of the document the current term comes from.
	XorPostList (PostList left_, PostList right_, MultiMatch *matcher_, Xapian::doccount dbsize_)
Private Member Functions
PostList *	advance_to_next_match (Xapian::weight w_min)
Private Attributes
Xapian::docid	lhead
Xapian::docid	rhead
Xapian::weight	lmax
Xapian::weight	rmax
Xapian::weight	minmax
Xapian::doccount	dbsize

Detailed Description

A postlist comprising two postlists XORed together.

This postlist returns a posting if and only if it is in one, and only one, of the sub-postlists. The weight for a posting is the weight of the sub-posting.

This postlist is only known to be useful as a "decay product" of other postlists. If you find an independent meaningful use, let us know...

Definition at line 40 of file xorpostlist.h.

Constructor & Destructor Documentation

XorPostList::XorPostList	(	PostList *	left_,
		PostList *	right_,
		MultiMatch *	matcher_,
		Xapian::doccount	dbsize_
	)

Definition at line 60 of file xorpostlist.cc.

References DEBUGCALL.

Member Function Documentation

PostList * XorPostList::advance_to_next_match ( Xapian::weight w_min ) [inline, private]

Definition at line 34 of file xorpostlist.cc.

References Xapian::PostingIterator::Internal::at_end(), DEBUGCALL, Xapian::PostingIterator::Internal::get_docid(), BranchPostList::l, lhead, BranchPostList::matcher, next_handling_prune(), BranchPostList::r, RETURN, and rhead.

Referenced by next(), and skip_to().

Xapian::doccount XorPostList::get_termfreq_max ( ) const [virtual]

Get an upper bound on the number of documents indexed by this term.

Implements Xapian::PostingIterator::Internal.

Definition at line 197 of file xorpostlist.cc.

References DEBUGCALL, Xapian::PostingIterator::Internal::get_termfreq_max(), BranchPostList::l, and BranchPostList::r.

Xapian::doccount XorPostList::get_termfreq_min ( ) const [virtual]

Get a lower bound on the number of documents indexed by this term.

Implements Xapian::PostingIterator::Internal.

Definition at line 204 of file xorpostlist.cc.

References DEBUGCALL, Xapian::PostingIterator::Internal::get_termfreq_max(), Xapian::PostingIterator::Internal::get_termfreq_min(), BranchPostList::l, and BranchPostList::r.

Xapian::doccount XorPostList::get_termfreq_est ( ) const [virtual]

Get an estimate of the number of documents indexed by this term.

It should always be true that: get_termfreq_min() <= get_termfreq_est() <= get_termfreq_max()

Implements Xapian::PostingIterator::Internal.

Definition at line 224 of file xorpostlist.cc.

References dbsize, DEBUGCALL, Xapian::PostingIterator::Internal::get_termfreq_est(), BranchPostList::l, BranchPostList::r, and RETURN.

Xapian::docid XorPostList::get_docid ( ) const [virtual]

Return the current docid.

Implements Xapian::PostingIterator::Internal.

Definition at line 236 of file xorpostlist.cc.

References Assert, DEBUGCALL, lhead, and rhead.

Xapian::weight XorPostList::get_weight ( ) const [virtual]

Return the weight contribution for the current position.

Implements Xapian::PostingIterator::Internal.

Definition at line 245 of file xorpostlist.cc.

References Assert, DEBUGCALL, Xapian::PostingIterator::Internal::get_weight(), BranchPostList::l, lhead, BranchPostList::r, and rhead.

Xapian::weight XorPostList::get_maxweight ( ) const [virtual]

Return an upper bound on what get_weight() can return.

Implements Xapian::PostingIterator::Internal.

Definition at line 256 of file xorpostlist.cc.

References DEBUGCALL, lmax, and rmax.

Referenced by recalc_maxweight().

Xapian::weight XorPostList::recalc_maxweight ( ) [virtual]

Recalculate the upper bound on what get_weight() can return.

If the tree has pruned, get_maxweight() may use cached values. Calling this method instead forces a full recalculation.

Implements Xapian::PostingIterator::Internal.

Definition at line 263 of file xorpostlist.cc.

References DEBUGCALL, get_maxweight(), BranchPostList::l, lmax, minmax, BranchPostList::r, Xapian::PostingIterator::Internal::recalc_maxweight(), and rmax.

PostList * XorPostList::next ( Xapian::weight w_min ) [virtual]

Advance the current position to the next document in the postlist.

The list starts before the first entry in the list, so next() must be called before any methods which need the context of the current position.

Parameters:

w_min

The minimum weight contribution that is needed (this is just a hint which PostList subclasses may ignore).

Returns:: If a non-NULL pointer is returned, then the caller should substitute the returned pointer for its pointer to us, and then delete us. This "pruning" can only happen for a non-leaf subclass of this class.

Implements Xapian::PostingIterator::Internal.

Definition at line 73 of file xorpostlist.cc.

References advance_to_next_match(), Assert, Xapian::PostingIterator::Internal::at_end(), dbsize, DEBUGCALL, DEBUGLINE, Xapian::PostingIterator::Internal::get_docid(), BranchPostList::l, lhead, lmax, BranchPostList::matcher, minmax, next_handling_prune(), BranchPostList::r, RETURN, rhead, and rmax.

PostList * XorPostList::skip_to	(	Xapian::docid	,
		Xapian::weight	w_min
	)			`[virtual]`

Skip forward to the specified docid.

If the specified docid isn't in the list, position ourselves on the first document after it (or at_end() if no greater docids are present).

Parameters:

w_min

The minimum weight contribution that is needed (this is just a hint which PostList subclasses may ignore).

Returns:: If a non-NULL pointer is returned, then the caller should substitute the returned pointer for its pointer to us, and then delete us. This "pruning" can only happen for a non-leaf subclass of this class.

Implements Xapian::PostingIterator::Internal.

Definition at line 133 of file xorpostlist.cc.

References advance_to_next_match(), Assert, dbsize, DEBUGCALL, DEBUGLINE, Xapian::PostingIterator::Internal::get_docid(), BranchPostList::l, lhead, lmax, BranchPostList::matcher, minmax, BranchPostList::r, RETURN, rhead, rmax, skip_to_handling_prune(), and AndNotPostList::sync_and_skip_to().