backends/brass/brass_inverter.h

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/* Copyright (C) 2009,2010 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 XAPIAN_INCLUDED_BRASS_INVERTER_H
#define XAPIAN_INCLUDED_BRASS_INVERTER_H

#include "xapian/types.h"

#include <map>
#include <string>

#include "omassert.h"
#include "str.h"
#include "xapian/error.h"

class BrassPostListTable;

const Xapian::termcount DELETED_POSTING = Xapian::termcount(-1);

class Inverter {
    friend class BrassPostListTable;

    class PostingChanges {
        friend class BrassPostListTable;

        Xapian::termcount_diff tf_delta;

        Xapian::termcount_diff cf_delta;

        std::map<Xapian::docid, Xapian::termcount> pl_changes;

      public:
        PostingChanges(Xapian::docid did, Xapian::termcount wdf)
            : tf_delta(1), cf_delta(Xapian::termcount_diff(wdf))
        {
            pl_changes.insert(std::make_pair(did, wdf));
        }

        PostingChanges(Xapian::docid did, Xapian::termcount wdf, bool)
            : tf_delta(-1), cf_delta(-Xapian::termcount_diff(wdf))
        {
            pl_changes.insert(std::make_pair(did, DELETED_POSTING));
        }

        PostingChanges(Xapian::docid did, Xapian::termcount old_wdf,
                       Xapian::termcount new_wdf)
            : tf_delta(0), cf_delta(Xapian::termcount_diff(new_wdf - old_wdf))
        {
            pl_changes.insert(std::make_pair(did, new_wdf));
        }

        void add_posting(Xapian::docid did, Xapian::termcount wdf) {
            ++tf_delta;
            cf_delta += wdf;
            // Add did to term's postlist
            pl_changes[did] = wdf;
        }

        void remove_posting(Xapian::docid did, Xapian::termcount wdf) {
            --tf_delta;
            cf_delta -= wdf;
            // Remove did from term's postlist.
            pl_changes[did] = DELETED_POSTING;
        }

        void update_posting(Xapian::docid did, Xapian::termcount old_wdf,
                            Xapian::termcount new_wdf) {
            cf_delta += new_wdf - old_wdf;
            pl_changes[did] = new_wdf;
        }

        Xapian::termcount_diff get_tfdelta() const { return tf_delta; }

        Xapian::termcount_diff get_cfdelta() const { return cf_delta; }
    };

    std::map<std::string, PostingChanges> postlist_changes;

  public:
    std::map<Xapian::docid, Xapian::termcount> doclen_changes;

  public:
    void add_posting(Xapian::docid did, const std::string & term,
                     Xapian::doccount wdf) {
        std::map<std::string, PostingChanges>::iterator i;
        i = postlist_changes.find(term);
        if (i == postlist_changes.end()) {
            postlist_changes.insert(
                std::make_pair(term, PostingChanges(did, wdf)));
        } else {
            i->second.add_posting(did, wdf);
        }
    }

    void remove_posting(Xapian::docid did, const std::string & term,
                        Xapian::doccount wdf) {
        std::map<std::string, PostingChanges>::iterator i;
        i = postlist_changes.find(term);
        if (i == postlist_changes.end()) {
            postlist_changes.insert(
                std::make_pair(term, PostingChanges(did, wdf, false)));
        } else {
            i->second.remove_posting(did, wdf);
        }
    }

    void update_posting(Xapian::docid did, const std::string & term,
                        Xapian::termcount old_wdf,
                        Xapian::termcount new_wdf) {
        std::map<std::string, PostingChanges>::iterator i;
        i = postlist_changes.find(term);
        if (i == postlist_changes.end()) {
            postlist_changes.insert(
                std::make_pair(term, PostingChanges(did, old_wdf, new_wdf)));
        } else {
            i->second.update_posting(did, old_wdf, new_wdf);
        }
    }

    void clear() {
        doclen_changes.clear();
        postlist_changes.clear();
    }

    void set_doclength(Xapian::docid did, Xapian::termcount doclen, bool add) {
        if (add) {
            Assert(doclen_changes.find(did) == doclen_changes.end() || doclen_changes[did] == DELETED_POSTING);
        }
        doclen_changes[did] = doclen;
    }

    void delete_doclength(Xapian::docid did) {
        Assert(doclen_changes.find(did) == doclen_changes.end() || doclen_changes[did] != DELETED_POSTING);
        doclen_changes[did] = DELETED_POSTING;
    }

    bool get_doclength(Xapian::docid did, Xapian::termcount & doclen) const  {
        std::map<Xapian::docid, Xapian::termcount>::const_iterator i;
        i = doclen_changes.find(did);
        if (i == doclen_changes.end())
            return false;
        if (rare(i->second == DELETED_POSTING))
            throw Xapian::DocNotFoundError("Document not found: " + str(did));
        doclen = i->second;
        return true;
    }

    void flush_doclengths(BrassPostListTable & table);

    void flush_post_list(BrassPostListTable & table, const std::string & term);

    void flush_all_post_lists(BrassPostListTable & table);

    void flush_post_lists(BrassPostListTable & table, const std::string & pfx);

    void flush(BrassPostListTable & table);

    Xapian::termcount_diff get_tfdelta(const std::string & term) const {
        std::map<std::string, PostingChanges>::const_iterator i;
        i = postlist_changes.find(term);
        if (i == postlist_changes.end())
            return 0;
        return i->second.get_tfdelta();
    }

    Xapian::termcount_diff get_cfdelta(const std::string & term) const {
        std::map<std::string, PostingChanges>::const_iterator i;
        i = postlist_changes.find(term);
        if (i == postlist_changes.end())
            return 0;
        return i->second.get_cfdelta();
    }
};

#endif // XAPIAN_INCLUDED_BRASS_INVERTER_H

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