parcel KinoSearch cnick Kino;

/** Consolidate index segments in the background.
 *
 * Adding documents to an index is usually fast, but every once in a while the
 * index must be compacted and an update takes substantially longer to
 * complete.  See L<KinoSearch::Docs::Cookbook::FastUpdates> for how to use
 * this class to control worst-case index update performance.
 *
 * As with L<Indexer|KinoSearch::Index::Indexer>, see
 * L<KinoSearch::Docs::FileLocking> if your index is on a shared volume.
 */
class KinoSearch::Index::BackgroundMerger cnick BGMerger
    inherits KinoSearch::Object::Obj {

    Schema            *schema;
    Folder            *folder;
    Segment           *segment;
    IndexManager      *manager;
    PolyReader        *polyreader;
    Snapshot          *snapshot;
    SegWriter         *seg_writer;
    DeletionsWriter   *del_writer;
    FilePurger        *file_purger;
    Lock              *write_lock;
    Lock              *merge_lock;
    CharBuf           *snapfile;
    Hash              *doc_maps;
    int64_t            cutoff;
    bool_t             optimize;
    bool_t             needs_commit;
    bool_t             prepared;

    public inert incremented BackgroundMerger*
    new(Obj *index, IndexManager *manager = NULL);

    /** Open a new BackgroundMerger.  
     *
     * @param index Either a string filepath or a Folder.
     * @param manager An IndexManager.  If not supplied, an IndexManager with
     * a 10-second write lock timeout will be created.
     */
    public inert BackgroundMerger*
    init(BackgroundMerger *self, Obj *index, IndexManager *manager = NULL);

    /** Optimize the index for search-time performance.  This may take a
     * while, as it can involve rewriting large amounts of data.
     */
    public void
    Optimize(BackgroundMerger *self);

    /** Commit any changes made to the index.  Until this is called, none of
     * the changes made during an indexing session are permanent.
     *
     * Calls Prepare_Commit() implicitly if it has not already been called.
     */
    public void
    Commit(BackgroundMerger *self);

    /** Perform the expensive setup for Commit() in advance, so that Commit()
     * completes quickly.  
     * 
     * Towards the end of Prepare_Commit(), the BackgroundMerger attempts to
     * re-acquire the write lock, which is then held until Commit() finishes
     * and releases it.
     */
    public void
    Prepare_Commit(BackgroundMerger *self);

    public void
    Destroy(BackgroundMerger *self);
}

/* Copyright 2007-2011 Marvin Humphrey
 *
 * This program is free software; you can redistribute it and/or modify
 * under the same terms as Perl itself.
 */