xapian-core/matcher/mergepostlist.h

   1 /** @file mergepostlist.h
   2  * @brief merge postlists from different databases
   3  */
   4 /* Copyright 1999,2000,2001 BrightStation PLC
   5  * Copyright 2002 Ananova Ltd
   6  * Copyright 2002,2003,2004,2005,2009,2011,2015,2016 Olly Betts
   7  * Copyright 2007 Lemur Consulting Ltd
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation; either version 2 of the
  12  * License, or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  22  * USA
  23  */
  24
  25 #ifndef OM_HGUARD_MERGEPOSTLIST_H
  26 #define OM_HGUARD_MERGEPOSTLIST_H
  27
  28 #include "api/postlist.h"
  29
  30 class MultiMatch;
  31 class ValueStreamDocument;
  32
  33 /** A postlist comprising postlists from different databases merged together.
  34  */
  35 class MergePostList : public PostList {
  36     private:
  37         // Prevent copying
  38         MergePostList(const MergePostList &);
  39         MergePostList & operator=(const MergePostList &);
  40
  41         double w_max;
  42
  43         vector<PostList *> plists;
  44
  45         int current;
  46
  47         /** The object which is using this postlist to perform
  48          *  a match.  This object needs to be notified when the
  49          *  tree changes such that the maximum weights need to be
  50          *  recalculated.
  51          */
  52         MultiMatch *matcher;
  53
  54         /** Document proxy used for valuestream caching.
  55          *
  56          *  We need to notify this when the subdatabase changes, as then the
  57          *  cached valuestreams need to be cleared as they will be for the
  58          *  wrong subdatabase.
  59          */
  60         ValueStreamDocument & vsdoc;
  61
  62     public:
  63         Xapian::termcount get_wdf() const;
  64         Xapian::doccount get_termfreq_max() const;
  65         Xapian::doccount get_termfreq_min() const;
  66         Xapian::doccount get_termfreq_est() const;
  67
  68         Xapian::docid get_docid() const;
  69         double get_weight() const;
  70         const string * get_sort_key() const;
  71         const string * get_collapse_key() const;
  72
  73         double get_maxweight() const;
  74
  75         double recalc_maxweight();
  76
  77         PostList *next(double w_min);
  78         PostList *skip_to(Xapian::docid did, double w_min);
  79         bool at_end() const;
  80
  81         string get_description() const;
  82
  83         /** Return the document length of the document the current term
  84          *  comes from.
  85          */
  86         virtual Xapian::termcount get_doclength() const;
  87
  88         /** Return the number of unique terms in the document. */
  89         virtual Xapian::termcount get_unique_terms() const;
  90
  91         Xapian::termcount count_matching_subqs() const;
  92
  93         MergePostList(const std::vector<PostList *> & plists_,
  94                       MultiMatch *matcher_,
  95                       ValueStreamDocument & vsdoc_)
  96             : plists(plists_), current(-1), matcher(matcher_), vsdoc(vsdoc_)
  97         { }
  98
  99         ~MergePostList();
 100 };
 101
 102 #endif /* OM_HGUARD_MERGEPOSTLIST_H */