root / tags / 1.0.8 / xapian-core / backends / flint / flint_database.h

/* flint_database.h: C++ class definition for flint database
 *
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2002,2003,2004,2005,2006,2007 Olly Betts
 *
 * 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 OM_HGUARD_FLINT_DATABASE_H
#define OM_HGUARD_FLINT_DATABASE_H

#include "database.h"
#include "flint_positionlist.h"
#include "flint_postlist.h"
#include "flint_record.h"
#include "flint_spelling.h"
#include "flint_synonym.h"
#include "flint_termlisttable.h"
#include "flint_values.h"
#include "flint_version.h"
#include "flint_lock.h"

#include "flint_types.h"

#include <map>

class FlintTermList;
class FlintAllDocsPostList;

const int XAPIAN_DB_READONLY = 0;

/** A backend designed for efficient indexing and retrieval, using
 *  compressed posting lists and a btree storage scheme.
 */
class FlintDatabase : public Xapian::Database::Internal {
    friend class FlintWritableDatabase;
    friend class FlintTermList;
    friend class FlintPostList;
    friend class FlintAllTermsList;
    friend class FlintAllDocsPostList;
    private:
        /** Directory to store databases in.
         */
        std::string db_dir;

        /** Whether the database is readonly.
         */
        bool readonly;

        /** The file describing the Flint database.
         *  This file has information about the format of the database
         *  which can't easily be stored in any of the individual tables.
         */
        FlintVersion version_file;

        /** Table storing posting lists.
         *
         *  Whenever an update is performed, this table is the first to be
         *  updated: therefore, its most recent revision number is the most
         *  recent anywhere in the database.
         */
        mutable FlintPostListTable postlist_table;

        /** Table storing position lists.
         */
        FlintPositionListTable position_table;

        /** Table storing term lists.
         */
        FlintTermListTable termlist_table;

        /** Table storing values.
         */
        FlintValueTable value_table;

        /** Table storing synonym data.
         */
        mutable FlintSynonymTable synonym_table;

        /** Table storing spelling correction data.
         */
        mutable FlintSpellingTable spelling_table;

        /** Table storing records.
         *
         *  Whenever an update is performed, this table is the last to be
         *  updated: therefore, its most recent revision number is the most
         *  recent consistent revision available.  If this table's most
         *  recent revision number is not available for all tables, there
         *  is no consistent revision available, and the database is corrupt.
         */
        FlintRecordTable record_table;

        /// Lock object.
        FlintLock lock;

        /** Total length of all documents including unflushed modifications. */
        mutable flint_totlen_t total_length;

        /** Highest document ID ever allocated by this database. */
        mutable Xapian::docid lastdocid;

        /// Read lastdocid and total_length from the postlist table.
        void read_metainfo();

        /** Return true if a database exists at the path specified for this
         *  database.
         */
        bool database_exists();

        /** Create new tables, and open them.
         *  Any existing tables will be removed first.
         */
        void create_and_open_tables(unsigned int blocksize);

        /** Open all tables at most recent consistent revision.
         *
         *  @exception Xapian::DatabaseCorruptError is thrown if there is no
         *  consistent revision available.
         */
        void open_tables_consistent();

        /** Get a write lock on the database, or throw an
         *  Xapian::DatabaseLockError if failure.
         */
        void get_database_write_lock();

        /** Open tables at specified revision number.
         *
         *  @exception Xapian::InvalidArgumentError is thrown if the specified
         *  revision is not available.
         */
        void open_tables(flint_revision_number_t revision);

        /** Get an object holding the revision number which the tables are
         *  opened at.
         *
         *  @return the current revision number.
         */
        flint_revision_number_t get_revision_number() const;

        /** Get an object holding the next revision number which should be
         *  used in the tables.
         *
         *  @return the next revision number.
         */
        flint_revision_number_t get_next_revision_number() const;

        /** Set the revision number in the tables.
         *
         *  This updates the disk tables so that the currently open revision
         *  becomes the specified revision number.
         *
         *  @param new_revision The new revision number to store.  This must
         *          be greater than the latest revision number (see
         *          get_latest_revision_number()), or undefined behaviour will
         *          result.
         */
        void set_revision_number(flint_revision_number_t new_revision);

        /** Re-open tables to recover from an overwritten condition,
         *  or just get most up-to-date version.
         */
        void reopen();

        /** Apply any outstanding changes to the tables.
         *
         *  If an error occurs during this operation, this will be signalled
         *  by an exception being thrown.  In this case the contents of the
         *  tables on disk will be left in an unmodified state (though possibly
         *  with increased revision numbers), and the outstanding changes will
         *  be lost.
         */
        void apply();

        /** Cancel any outstanding changes to the tables.
         */
        void cancel();

    public:
        /** Create and open a flint database.
         *
         *  @exception Xapian::DatabaseCorruptError is thrown if there is no
         *             consistent revision available.
         *
         *  @exception Xapian::DatabaseOpeningError thrown if database can't
         *             be opened.
         *
         *  @exception Xapian::DatabaseVersionError thrown if database is in an
         *             unsupported format.  This implies that the database was
         *             created by an older or newer version of Xapian.
         *
         *  @param dbdir directory holding flint tables
         *
         *  @param block_size Block size, in bytes, to use when creating
         *                    tables.  This is only important, and has the
         *                    correct value, when the database is being
         *                    created.
         */
        FlintDatabase(const string &db_dir_, int action = XAPIAN_DB_READONLY,
                       unsigned int block_size = 0u);

        ~FlintDatabase();

        /** Virtual methods of Database::Internal. */
        //@{
        Xapian::doccount  get_doccount() const;
        Xapian::docid get_lastdocid() const;
        Xapian::doclength get_avlength() const;
        Xapian::doclength get_doclength(Xapian::docid did) const;
        Xapian::doccount get_termfreq(const string & tname) const;
        Xapian::termcount get_collection_freq(const string & tname) const;
        bool term_exists(const string & tname) const;
        bool has_positions() const;

        LeafPostList * open_post_list(const string & tname) const;
        Xapian::Document::Internal * open_document(Xapian::docid did, bool lazy = false) const;

        PositionList * open_position_list(Xapian::docid did, const string & term) const;
        TermList * open_term_list(Xapian::docid did) const;
        TermList * open_allterms(const string & prefix) const;

        TermList * open_spelling_termlist(const string & word) const;
        TermList * open_spelling_wordlist() const;
        Xapian::doccount get_spelling_frequency(const string & word) const;

        TermList * open_synonym_termlist(const string & term) const;
        TermList * open_synonym_keylist(const string & prefix) const;

        string get_metadata(const string & key) const;
        //@}
};

/** A writable flint database.
 */
class FlintWritableDatabase : public FlintDatabase {
        /** Unflushed changes to term frequencies and collection frequencies. */
        mutable map<string, pair<Xapian::termcount_diff, Xapian::termcount_diff> >
                freq_deltas;

        /** Document lengths of new and modified documents which haven't been flushed yet. */
        mutable map<Xapian::docid, Xapian::termcount> doclens;

        /// Modifications to posting lists.
        mutable map<string, map<Xapian::docid,
                                pair<char, Xapian::termcount> > > mod_plists;

        /** The number of documents added, deleted, or replaced since the last
         *  flush.
         */
        mutable Xapian::doccount change_count;

        /// If change_count reaches this threshold we automatically flush.
        Xapian::doccount flush_threshold;

        /// Flush any unflushed postlist changes, but don't commit them.
        void flush_postlist_changes() const;

        //@{
        /** Implementation of virtual methods: see Database::Internal for
         *  details.
         */
        void flush();

        /** Cancel pending modifications to the database. */
        void cancel();

        Xapian::docid add_document(const Xapian::Document & document);
        Xapian::docid add_document_(Xapian::docid did, const Xapian::Document & document);
        // Stop the default implementation of delete_document(term) and
        // replace_document(term) from being hidden.  This isn't really
        // a problem as we only try to call them through the base class
        // (where they aren't hidden) but some compilers generate a warning
        // about the hiding.
#if (!defined __GNUC__ && !defined _MSC_VER) || __GNUC__ > 2
        using Xapian::Database::Internal::delete_document;
        using Xapian::Database::Internal::replace_document;
#endif
        void delete_document(Xapian::docid did);
        void replace_document(Xapian::docid did, const Xapian::Document & document);
        //@}

    public:
        /** Create and open a writable flint database.
         *
         *  @exception Xapian::DatabaseOpeningError thrown if database can't
         *             be opened.
         *
         *  @exception Xapian::DatabaseVersionError thrown if database is in an
         *             unsupported format.  This implies that the database was
         *             created by an older or newer version of Xapian.
         *
         *  @param dir directory holding flint tables
         */
        FlintWritableDatabase(const string &dir, int action, int block_size);

        ~FlintWritableDatabase();

        /** Virtual methods of Database::Internal. */
        //@{
        Xapian::doclength get_doclength(Xapian::docid did) const;
        Xapian::doccount get_termfreq(const string & tname) const;
        Xapian::termcount get_collection_freq(const string & tname) const;
        bool term_exists(const string & tname) const;

        LeafPostList * open_post_list(const string & tname) const;
        TermList * open_allterms(const string & prefix) const;

        void add_spelling(const string & word, Xapian::termcount freqinc) const;
        void remove_spelling(const string & word, Xapian::termcount freqdec) const;
        TermList * open_spelling_wordlist() const;

        TermList * open_synonym_keylist(const string & prefix) const;
        void add_synonym(const string & word, const string & synonym) const;
        void remove_synonym(const string & word, const string & synonym) const;
        void clear_synonyms(const string & word) const;

        void set_metadata(const string & key, const string & value);
        //@}
};

#endif /* OM_HGUARD_FLINT_DATABASE_H */