annotate rdf/SimpleSPARQLQuery.h @ 492:23945cdd7161

* Update RDF query stuff again so as to set up a temporary datastore
  each time we want to query over an rdf file, instead of using rasqal
  against the file.  Seems the only way to avoid threading and storage
  management issues when trying to load from a single-source file and
  perform queries against our main datastore at the same time.  Maybe.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2008 QMUL.
   
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _SIMPLE_SPARQL_QUERY_H_
#define _SIMPLE_SPARQL_QUERY_H_

#include <QString>
#include <map>
#include <vector>

class ProgressReporter;

class SimpleSPARQLQuery
{
public:
    enum ValueType { NoValue, URIValue, LiteralValue, BlankValue };

    struct Value {
        Value() : type(NoValue), value() { }
        Value(ValueType t, QString v) : type(t), value(v) { }
        ValueType type;
        QString value;
    };

    typedef std::map<QString, Value> KeyValueMap;
    typedef std::vector<KeyValueMap> ResultList;

    /**
     * QueryType specifies the context in which the query will be
     * evaluated.  SimpleSPARQLQuery maintains a general global data
     * model, into which data can be loaded using addSourceToModel(),
     * as well as permitting one-time queries directly on data sources
     * identified by URL.
     *
     * The query type QueryFromModel indicates a query to be evaluated
     * over the general global model; the query type
     * QueryFromSingleSource indicates that the query should be
     * evaluated in the context of a model generated solely by parsing
     * the FROM url found in the query.
     *
     * Even in QueryFromSingleSource mode, the parsed data remains in
     * memory and will be reused in subsequent queries with the same
     * mode and FROM url.  To release data loaded in this way once all
     * queries across it are complete, pass the said FROM url to
     * closeSingleSource().
     */
    enum QueryType {
        QueryFromModel,
        QueryFromSingleSource
    };

    /**
     * Construct a query of the given type (indicating the data model
     * context for the query) using the given SPARQL query content.
     */
    SimpleSPARQLQuery(QueryType type, QString query);
    ~SimpleSPARQLQuery();

    /**
     * Add the given URI to the general global model used for
     * QueryFromModel queries.
     */
    static bool addSourceToModel(QString sourceUri);

    /**
     * Release any data that has been loaded from the given source as
     * part of a QueryFromSingleSource query with this source in the
     * FROM clause.  Note this will not prevent any subsequent queries
     * on the source from working -- it will just make them slower as
     * the data will need to be re-parsed.
     */
    static void closeSingleSource(QString sourceUri);

    void setProgressReporter(ProgressReporter *reporter);
    bool wasCancelled() const;
    
    ResultList execute();

    bool isOK() const;
    QString getErrorString() const;

    /**
     * Construct and execute a query, and return the first result
     * value for the given binding.
     */
    static Value singleResultQuery(QueryType type,
                                   QString query,
                                   QString binding);

protected:
    class Impl;
    Impl *m_impl;
};

#endif