qgsqueryresultmodel.h

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/***************************************************************************
  qgsqueryresultmodel.h - QgsQueryResultModel
 
 ---------------------
 begin                : 24.12.2020
 copyright            : (C) 2020 by Alessandro Pasotti
 email                : [email protected]
 ***************************************************************************
 *                                                                         *
 *   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.                                   *
 *                                                                         *
 ***************************************************************************/
#ifndef QgsQueryResultModel_H
#define QgsQueryResultModel_H
 
#include "qgis_core.h"
#include "qgis_sip.h"
#include "qgsabstractdatabaseproviderconnection.h"
 
#include <QAbstractTableModel>
#include <QThread>

 
#ifndef SIP_RUN

class QgsQueryResultFetcher : public QObject
{
    Q_OBJECT
 
  public:
    QgsQueryResultFetcher( const QgsAbstractDatabaseProviderConnection::QueryResult *queryResult )
      : mQueryResult( queryResult )
    {}

    void fetchRows( long long maxRows = -1 );

    void stopFetching();
 
  signals:

    void rowsReady( const QList<QList<QVariant>> &newRows );

    void fetchingComplete();
 
  private:
    const QgsAbstractDatabaseProviderConnection::QueryResult *mQueryResult = nullptr;
    QAtomicInt mStopFetching = 0;
    // Number of rows rows to fetch before emitting rowsReady
    static const int ROWS_BATCH_COUNT;
};
 
#endif

 

class CORE_EXPORT QgsQueryResultModel : public QAbstractTableModel
{
    Q_OBJECT
  public:
    QgsQueryResultModel( const QgsAbstractDatabaseProviderConnection::QueryResult &queryResult, QObject *parent = nullptr );
 
    ~QgsQueryResultModel() override;
 
    // QAbstractItemModel interface
  public:
    int rowCount( const QModelIndex &parent ) const override;
    int columnCount( const QModelIndex &parent ) const override;
    QVariant data( const QModelIndex &index, int role ) const override;
    QVariant headerData( int section, Qt::Orientation orientation, int role ) const override;
 
    void fetchMore( const QModelIndex &parent ) override;
    bool canFetchMore( const QModelIndex &parent ) const override;

    QStringList columns() const;

    QgsAbstractDatabaseProviderConnection::QueryResult queryResult() const;
 
  public slots:

    void rowsReady( const QList<QList<QVariant> > &rows );

    void cancel();
 
 
  signals:

    void fetchingComplete();

    void fetchMoreRows( qlonglong maxRows );

    void fetchingStarted();
 
  private:
    QgsAbstractDatabaseProviderConnection::QueryResult mQueryResult;
    QStringList mColumns;
    QThread mWorkerThread;
    std::unique_ptr<QgsQueryResultFetcher> mWorker;
    QList<QVariantList> mRows;

    static const int FETCH_MORE_ROWS_COUNT;
};
 
#endif // qgsqueryresultmodel.h