xapian-core/api/rsetinternal.h

   1 /** @file rsetinternal.h
   2  * @brief Set of documents judged as relevant
   3  */
   4 /* Copyright (C) 2017 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  17  */
  18
  19 #ifndef XAPIAN_INCLUDED_RSETINTERNAL_H
  20 #define XAPIAN_INCLUDED_RSETINTERNAL_H
  21
  22 #include <xapian/rset.h>
  23
  24 #include "backends/multi.h"
  25
  26 #include <set>
  27 #include <vector>
  28
  29 namespace Xapian {
  30
  31 class RSet::Internal : public Xapian::Internal::intrusive_base {
  32   public:
  33     // We want to be able to iterate the contents in docid order, and we don't
  34     // expect people to mark vast numbers of documents as relevant, so use
  35     // std::set rather than std::unordered_set.
  36     std::set<Xapian::docid> docs;
  37
  38     void shard(size_t n_shards, std::vector<Xapian::RSet>& rsets) {
  39         if (n_shards == 1 || docs.empty()) {
  40             // Either there's a single database (in which case we just need
  41             // to return ourself as the sharded RSet), or there are no relevance
  42             // judgements (in which case we can use ourself as the internals for
  43             // all the empty sharded RSets).
  44             rsets.resize(n_shards, RSet(this));
  45             return;
  46         }
  47
  48         // Using resize() here would result in all the entries having the same
  49         // internals.
  50         rsets.reserve(n_shards);
  51         for (size_t i = 0; i < n_shards; ++i) {
  52             rsets.emplace_back(RSet());
  53         }
  54
  55         for (auto&& did : docs) {
  56             Xapian::docid shard_did = shard_docid(did, n_shards);
  57             rsets[shard_number(did, n_shards)].add_document(shard_did);
  58         }
  59     }
  60 };
  61
  62 }
  63
  64 #endif // XAPIAN_INCLUDED_RSETINTERNAL_H