backends/inmemory/inmemory_database.h

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/* inmemory_database.h: C++ class definition for multiple database access
 *
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2002,2003,2004,2005,2006,2007 Olly Betts
 * Copyright 2006 Richard Boulton
 *
 * 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_INMEMORY_DATABASE_H
#define OM_HGUARD_INMEMORY_DATABASE_H

#include "leafpostlist.h"
#include "termlist.h"
#include "database.h"
#include <map>
#include <vector>
#include <algorithm>
#include <xapian/document.h>
#include "inmemory_positionlist.h"
#include <omassert.h>

using namespace std;

// Class representing a posting (a term/doc pair, and
// all the relevant positional information, is a single posting)
class InMemoryPosting {
    public:
        Xapian::docid did;
        bool valid;
        vector<Xapian::termpos> positions; // Sorted vector of positions
        Xapian::termcount wdf;

        // Merge two postings (same term/doc pair, new positional info)
        void merge(const InMemoryPosting & post) {
            Assert(did == post.did);

            positions.insert(positions.end(),
                             post.positions.begin(),
                             post.positions.end());
            // FIXME - inefficient - use merge (and list<>)?
            sort(positions.begin(), positions.end());
        }
};

class InMemoryTermEntry {
    public:
        string tname;
        vector<Xapian::termpos> positions; // Sorted vector of positions
        Xapian::termcount wdf;

        // Merge two postings (same term/doc pair, new positional info)
        void merge(const InMemoryTermEntry & post) {
            Assert(tname == post.tname);

            positions.insert(positions.end(),
                             post.positions.begin(),
                             post.positions.end());
            // FIXME - inefficient - use merge (and list<>)?
            sort(positions.begin(), positions.end());
        }
};

// Compare by document ID
class InMemoryPostingLessThan {
    public:
        int operator() (const InMemoryPosting &p1, const InMemoryPosting &p2)
        {
            return p1.did < p2.did;
        }
};

// Compare by termname
class InMemoryTermEntryLessThan {
    public:
        int operator() (const InMemoryTermEntry&p1, const InMemoryTermEntry&p2)
        {
            return p1.tname < p2.tname;
        }
};

// Class representing a term and the documents indexing it
class InMemoryTerm {
    public:
        // Sorted list of documents indexing this term.
        vector<InMemoryPosting> docs;

        Xapian::termcount term_freq;
        Xapian::termcount collection_freq;

        InMemoryTerm() : term_freq(0), collection_freq(0) {}

        void add_posting(const InMemoryPosting & post);
};

class InMemoryDoc {
    public:
        bool is_valid;
        // Sorted list of terms indexing this document.
        vector<InMemoryTermEntry> terms;

        /* Initialise invalid by default, so that resizing the termlist array
         * doesn't create valid documents. */
        InMemoryDoc() : is_valid(false) {}

        // Initialise specifying validity.
        InMemoryDoc(bool is_valid_) : is_valid(is_valid_) {}

        void add_posting(const InMemoryTermEntry & post);
};

class InMemoryDatabase;

class InMemoryPostList : public LeafPostList {
    friend class InMemoryDatabase;
    private:
        vector<InMemoryPosting>::const_iterator pos;
        vector<InMemoryPosting>::const_iterator end;
        Xapian::doccount termfreq;
        bool started;

        InMemoryPositionList mypositions;

        Xapian::Internal::RefCntPtr<const InMemoryDatabase> db;

        InMemoryPostList(Xapian::Internal::RefCntPtr<const InMemoryDatabase> db,
                         const InMemoryTerm & term);
    public:
        Xapian::doccount get_termfreq() const;

        Xapian::docid       get_docid() const;     // Gets current docid
        Xapian::doclength   get_doclength() const; // Length of current document
        Xapian::termcount   get_wdf() const;          // Within Document Frequency
        PositionList * read_position_list();
        PositionList * open_position_list() const;

        PostList *next(Xapian::weight w_min); // Moves to next docid

        PostList *skip_to(Xapian::docid did, Xapian::weight w_min); // Moves to next docid >= specified docid

        // True if we're off the end of the list.
        bool at_end() const;

        string get_description() const;
};

class InMemoryAllDocsPostList : public LeafPostList {
    friend class InMemoryDatabase;
    private:
        Xapian::docid did;

        Xapian::Internal::RefCntPtr<const InMemoryDatabase> db;

        InMemoryAllDocsPostList(Xapian::Internal::RefCntPtr<const InMemoryDatabase> db);
    public:
        Xapian::doccount get_termfreq() const;

        Xapian::docid       get_docid() const;     // Gets current docid
        Xapian::doclength   get_doclength() const; // Length of current document
        Xapian::termcount   get_wdf() const;       // Within Document Frequency
        PositionList * read_position_list();
        PositionList * open_position_list() const;

        PostList *next(Xapian::weight w_min);      // Moves to next docid

        PostList *skip_to(Xapian::docid did, Xapian::weight w_min); // Moves to next docid >= specified docid

        // True if we're off the end of the list
        bool at_end() const;

        string get_description() const;
};

// Term List
class InMemoryTermList : public TermList {
    friend class InMemoryDatabase;
    private:
        vector<InMemoryTermEntry>::const_iterator pos;
        vector<InMemoryTermEntry>::const_iterator end;
        Xapian::termcount terms;
        bool started;

        Xapian::Internal::RefCntPtr<const InMemoryDatabase> db;
        Xapian::docid did;
        Xapian::doclength document_length;

        InMemoryTermList(Xapian::Internal::RefCntPtr<const InMemoryDatabase> db, Xapian::docid did,
                         const InMemoryDoc & doc,
                         Xapian::doclength len);
    public:
        Xapian::termcount get_approx_size() const;

        void accumulate_stats(Xapian::Internal::ExpandStats & stats) const;

        string get_termname() const;
        Xapian::termcount get_wdf() const; // Number of occurrences of term in current doc
        Xapian::doccount get_termfreq() const;  // Number of docs indexed by term
        TermList * next();
        bool at_end() const;
        Xapian::termcount positionlist_count() const;
        Xapian::PositionIterator positionlist_begin() const;
};

class InMemoryDatabase : public Xapian::Database::Internal {
    friend class InMemoryAllDocsPostList;

    map<string, InMemoryTerm> postlists;
    vector<InMemoryDoc> termlists;
    vector<std::string> doclists;
    vector<std::map<Xapian::valueno, string> > valuelists;

    vector<Xapian::doclength> doclengths;

    std::map<string, string> metadata;

    Xapian::doccount totdocs;

    Xapian::doclength totlen;

    bool positions_present;

    // Stop copy / assignment being allowed
    InMemoryDatabase& operator=(const InMemoryDatabase &);
    InMemoryDatabase(const InMemoryDatabase &);

    void make_term(const string & tname);

    bool doc_exists(Xapian::docid did) const;
    Xapian::docid make_doc(const string & docdata);

    /* The common parts of add_doc and replace_doc */
    void finish_add_doc(Xapian::docid did, const Xapian::Document &document);
    void add_values(Xapian::docid did, const map<Xapian::valueno, string> &values_);

    void make_posting(InMemoryDoc * doc,
                      const string & tname,
                      Xapian::docid did,
                      Xapian::termpos position,
                      Xapian::termcount wdf,
                      bool use_position = true);


    void flush();
    void cancel();

    Xapian::docid add_document(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:
    InMemoryDatabase();

    ~InMemoryDatabase();

    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;
    TermList * open_term_list(Xapian::docid did) const;
    Xapian::Document::Internal * open_document(Xapian::docid did, bool lazy = false) const;

    std::string get_metadata(const std::string & key) const;
    void set_metadata(const std::string & key, const std::string & value);

    Xapian::termcount positionlist_count(Xapian::docid did,
                                         const string & tname) const;
    PositionList * open_position_list(Xapian::docid did,
                                      const string & tname) const;
    TermList * open_allterms(const string & prefix) const;
};

#endif /* OM_HGUARD_INMEMORY_DATABASE_H */

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