xapian-core/include/xapian/compactor.h

   1 /** @file
   2  * @brief Compact a database, or merge and compact several.
   3  */
   4 /* Copyright (C) 2003,2004,2005,2006,2007,2008,2009,2010,2011,2013,2014,2015,2018 Olly Betts
   5  * Copyright (C) 2008 Lemur Consulting Ltd
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  20  * USA
  21  */
  22
  23 #ifndef XAPIAN_INCLUDED_COMPACTOR_H
  24 #define XAPIAN_INCLUDED_COMPACTOR_H
  25
  26 #if !defined XAPIAN_IN_XAPIAN_H && !defined XAPIAN_LIB_BUILD
  27 # error Never use <xapian/compactor.h> directly; include <xapian.h> instead.
  28 #endif
  29
  30 #include <xapian/constants.h>
  31 #include <xapian/visibility.h>
  32 #include <string>
  33
  34 namespace Xapian {
  35
  36 class Database;
  37
  38 /** Compact a database, or merge and compact several.
  39  */
  40 class XAPIAN_VISIBILITY_DEFAULT Compactor {
  41   public:
  42     /** Compaction level. */
  43     typedef enum {
  44         /** Don't split items unnecessarily. */
  45         STANDARD = 0,
  46         /** Split items whenever it saves space (the default). */
  47         FULL = 1,
  48         /** Allow oversize items to save more space (not recommended if you
  49          *  ever plan to update the compacted database). */
  50         FULLER = 2
  51     } compaction_level;
  52
  53     Compactor() {}
  54
  55     virtual ~Compactor();
  56
  57     /** Update progress.
  58      *
  59      *  Subclass this method if you want to get progress updates during
  60      *  compaction.  This is called for each table first with empty status,
  61      *  And then one or more times with non-empty status.
  62      *
  63      *  The default implementation does nothing.
  64      *
  65      *  @param table    The table currently being compacted.
  66      *  @param status   A status message.
  67      */
  68     virtual void
  69     set_status(const std::string & table, const std::string & status);
  70
  71     /** Resolve multiple user metadata entries with the same key.
  72      *
  73      *  When merging, if the same user metadata key is set in more than one
  74      *  input, then this method is called to allow this to be resolving in
  75      *  an appropriate way.
  76      *
  77      *  The default implementation just returns tags[0].
  78      *
  79      *  For multipass this will currently get called multiple times for the
  80      *  same key if there are duplicates to resolve in each pass, but this
  81      *  may change in the future.
  82      *
  83      *  Since 1.4.6, an implementation of this method can return an empty
  84      *  string to indicate that the appropriate result is to not set a value
  85      *  for this user metadata key in the output database.  In older versions,
  86      *  you should not return an empty string.
  87      *
  88      *  @param key      The metadata key with duplicate entries.
  89      *  @param num_tags How many tags there are.
  90      *  @param tags     An array of num_tags strings containing the tags to
  91      *                  merge.
  92      */
  93     virtual std::string
  94     resolve_duplicate_metadata(const std::string & key,
  95                                size_t num_tags, const std::string tags[]);
  96 };
  97
  98 }
  99
 100 #endif /* XAPIAN_INCLUDED_COMPACTOR_H */