AndMaybePostList Class Reference

A postlist with weights modified by another postlist. More...

#include <andmaybepostlist.h>

Inheritance diagram for AndMaybePostList:

[legend]Collaboration diagram for AndMaybePostList:


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.
	AndMaybePostList (PostList left_, PostList right_, MultiMatch *matcher_, Xapian::doccount dbsize_)
	AndMaybePostList (PostList left_, PostList right_, MultiMatch *matcher_, Xapian::doccount dbsize_, Xapian::docid lhead_, Xapian::docid rhead_)
	Constructor for use by decomposing OrPostList.
Private Member Functions
PostList *	process_next_or_skip_to (Xapian::weight w_min, PostList *ret)
Private Attributes
Xapian::doccount	dbsize
Xapian::docid	lhead
Xapian::docid	rhead
Xapian::weight	lmax
Xapian::weight	rmax

Detailed Description

A postlist with weights modified by another postlist.

This postlist returns a posting if and only if it is in the left sub-postlist.

If the posting does not occur in the right postlist, the weight for the posting is simply that in the left postlist. If the posting occurs in both postlists, the weight for the posting is the sum of the weights in the sub-postlists.

This type of postlist is useful for specifying a set of terms which must appear in the query result: these terms can be specified as the left hand argument, with the rest of the query being on the right hand side, and having the effect of modifying the weights.

The postlist is also used as a "decay product" of other postlist types during the match process: when a postlist can no longer cause a document to enter the mset on its own, but can influence relative rankings, it may be combined using one of these.

Definition at line 54 of file andmaybepostlist.h.

Constructor & Destructor Documentation

AndMaybePostList::AndMaybePostList	(	PostList *	left_,
		PostList *	right_,
		MultiMatch *	matcher_,
		Xapian::doccount	dbsize_
	)			`[inline]`

Definition at line 83 of file andmaybepostlist.h.

AndMaybePostList::AndMaybePostList	(	PostList *	left_,
		PostList *	right_,
		MultiMatch *	matcher_,
		Xapian::doccount	dbsize_,
		Xapian::docid	lhead_,
		Xapian::docid	rhead_
	)			`[inline]`

Constructor for use by decomposing OrPostList.

Definition at line 94 of file andmaybepostlist.h.

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

Member Function Documentation

PostList * AndMaybePostList::process_next_or_skip_to	(	Xapian::weight	w_min,
		PostList *	ret
	)			`[private]`

Definition at line 31 of file andmaybepostlist.cc.

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

Referenced by next(), and skip_to().

Xapian::doccount AndMaybePostList::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 92 of file andmaybepostlist.cc.

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

Xapian::doccount AndMaybePostList::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 100 of file andmaybepostlist.cc.

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

Xapian::doccount AndMaybePostList::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 108 of file andmaybepostlist.cc.

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

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

Return the current docid.

Implements Xapian::PostingIterator::Internal.

Definition at line 116 of file andmaybepostlist.cc.

References Assert, DEBUGCALL, lhead, RETURN, and rhead.

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

Return the weight contribution for the current position.

Implements Xapian::PostingIterator::Internal.

Definition at line 125 of file andmaybepostlist.cc.

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

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

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

Implements Xapian::PostingIterator::Internal.

Definition at line 135 of file andmaybepostlist.cc.

References DEBUGCALL, lmax, RETURN, and rmax.

Referenced by recalc_maxweight().

Xapian::weight AndMaybePostList::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 142 of file andmaybepostlist.cc.

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

PostList * AndMaybePostList::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 55 of file andmaybepostlist.cc.

References dbsize, DEBUGCALL, DEBUGLINE, BranchPostList::l, lhead, lmax, BranchPostList::matcher, Xapian::PostingIterator::Internal::next(), process_next_or_skip_to(), BranchPostList::r, RETURN, rhead, rmax, and skip_to_handling_prune().

PostList * AndMaybePostList::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 71 of file andmaybepostlist.cc.

References dbsize, DEBUGCALL, DEBUGLINE, BranchPostList::l, lhead, lmax, BranchPostList::matcher, process_next_or_skip_to(), BranchPostList::r, RETURN, rhead, rmax, Xapian::PostingIterator::Internal::skip_to(), and skip_to_handling_prune().