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/** @file leafpostlist.h
* @brief Abstract base class for leaf postlists.
*/
/* Copyright (C) 2007,2009,2011,2013,2015,2016 Olly Betts
* Copyright (C) 2009 Lemur Consulting Ltd
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef XAPIAN_INCLUDED_LEAFPOSTLIST_H
#define XAPIAN_INCLUDED_LEAFPOSTLIST_H
#include "postlist.h"
#include <string>
namespace Xapian {
class Weight;
}
/** Abstract base class for leaf postlists.
*
* This class provides the following features in addition to the PostList
* class:
*/
class LeafPostList : public PostList {
/// Don't allow assignment.
void operator=(const LeafPostList &);
/// Don't allow copying.
LeafPostList(const LeafPostList &);
protected:
const Xapian::Weight * weight;
bool need_doclength, need_unique_terms;
/// The term name for this postlist (empty for an alldocs postlist).
std::string term;
/// Only constructable as a base class for derived classes.
explicit LeafPostList(const std::string & term_)
: weight(0), need_doclength(false), need_unique_terms(false),
term(term_) { }
public:
~LeafPostList();
/** Set the weighting scheme to use during matching.
*
* If this isn't called, get_weight() and get_maxweight() will both
* return 0.
*
* You should not call this more than once on a particular object.
*
* @param weight_ The weighting object to use. Must not be NULL.
*/
void set_termweight(const Xapian::Weight * weight_);
double resolve_lazy_termweight(Xapian::Weight * weight_,
Xapian::Weight::Internal * stats,
Xapian::termcount qlen,
Xapian::termcount wqf,
double factor)
{
weight_->init_(*stats, qlen, term, wqf, factor);
// There should be an existing LazyWeight set already.
Assert(weight);
const Xapian::Weight * const_weight_ = weight_;
std::swap(weight, const_weight_);
delete const_weight_;
need_doclength = weight->get_sumpart_needs_doclength_();
stats->termfreqs[term].max_part += weight->get_maxpart();
return stats->termfreqs[term].max_part;
}
/** Return the exact term frequency.
*
* Leaf postlists have an exact termfreq, which get_termfreq_min(),
* get_termfreq_max(), and get_termfreq_est() all report.
*/
virtual Xapian::doccount get_termfreq() const = 0;
Xapian::doccount get_termfreq_min() const;
Xapian::doccount get_termfreq_max() const;
Xapian::doccount get_termfreq_est() const;
double get_maxweight() const;
double get_weight() const;
double recalc_maxweight();
TermFreqs get_termfreq_est_using_stats(
const Xapian::Weight::Internal & stats) const;
Xapian::termcount count_matching_subqs() const;
void gather_position_lists(OrPositionList* orposlist);
/** Open another postlist from the same database.
*
* @param term_ The term to open a postlist for. If term_ is near to
* this postlist's term, then this can be a lot more
* efficient (and if it isn't very near, there's not
* much of a penalty). Using this method can make a
* wildcard expansion much more memory efficient.
*
* @return The new postlist object, or NULL if not supported
* (in which case the caller should probably the postlist
* via the database instead).
*/
virtual LeafPostList * open_nearby_postlist(const std::string & term_) const;
/** Set the term name.
*
* This is useful when we optimise a term matching all documents to an
* all documents postlist under OP_SYNONYM, as the term name is used by
* LeafPostList::get_termfreq_est_using_stats() to locate the appropriate
* TermFreqs object.
*/
void set_term(const std::string & term_) { term = term_; }
};
#endif // XAPIAN_INCLUDED_LEAFPOSTLIST_H
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