qgsaggregatecalculator.h

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/***************************************************************************
                             qgsaggregatecalculator.h
                             ------------------------
    begin                : May 2016
    copyright            : (C) 2016 by Nyall Dawson
    email                : nyall dot dawson at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   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 QGSAGGREGATECALCULATOR_H
#define QGSAGGREGATECALCULATOR_H
 
#include "qgis_core.h"
#include "qgsstatisticalsummary.h"
#include "qgsfeaturerequest.h"
#include <QVariant>
#include "qgsfeatureid.h"
 
 
class QgsFeatureIterator;
class QgsExpression;
class QgsVectorLayer;
class QgsExpressionContext;
 
class CORE_EXPORT QgsAggregateCalculator
{
  public:
 
    struct AggregateInfo
    {
      QString function;
      QString name;
      QSet<QVariant::Type> supportedTypes;
    };
 
    struct AggregateParameters
    {
 
      QString filter;
 
      QString delimiter;
 
      QgsFeatureRequest::OrderBy orderBy;
    };
 
    QgsAggregateCalculator( const QgsVectorLayer *layer );
 
    QString lastError() const { return mLastError; }
 
    const QgsVectorLayer *layer() const;
 
    void setParameters( const AggregateParameters &parameters );
 
    void setFilter( const QString &filterExpression ) { mFilterExpression = filterExpression; }
 
    void setFidsFilter( const QgsFeatureIds &fids );
 
    QString filter() const { return mFilterExpression; }
 
    void setDelimiter( const QString &delimiter ) { mDelimiter = delimiter; }
 
    QString delimiter() const { return mDelimiter; }
 
    QVariant calculate( Qgis::Aggregate aggregate, const QString &fieldOrExpression,
                        QgsExpressionContext *context = nullptr, bool *ok = nullptr, QgsFeedback *feedback = nullptr ) const;
 
    static Qgis::Aggregate stringToAggregate( const QString &string, bool *ok = nullptr );
 
    static QString displayName( Qgis::Aggregate aggregate );
 
    static QList< QgsAggregateCalculator::AggregateInfo > aggregates();
 
  private:
 
    const QgsVectorLayer *mLayer = nullptr;
 
    QString mFilterExpression;
 
    QgsFeatureRequest::OrderBy mOrderBy;
 
    QString mDelimiter;
 
    QgsFeatureIds mFidsFilter;
 
    //trigger variable
    bool mFidsSet = false;
 
    mutable QString mLastError;
 
    static Qgis::Statistic numericStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
    static Qgis::StringStatistic stringStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
    static Qgis::DateTimeStatistic dateTimeStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
 
    static QVariant calculateNumericAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, Qgis::Statistic stat );
 
    static QVariant calculateStringAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, Qgis::StringStatistic stat );
 
    static QVariant calculateDateTimeAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, Qgis::DateTimeStatistic stat );
    static QVariant calculateGeometryAggregate( QgsFeatureIterator &fit, QgsExpression *expression, QgsExpressionContext *context );
 
    static QVariant calculateArrayAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context );
 
    static QVariant calculate( Qgis::Aggregate aggregate, QgsFeatureIterator &fit, QVariant::Type resultType, int userType,
                               int attr, QgsExpression *expression,
                               const QString &delimiter,
                               QgsExpressionContext *context, bool *ok = nullptr, QString *error = nullptr );
    static QVariant concatenateStrings( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
                                        QgsExpressionContext *context, const QString &delimiter, bool unique = false );
 
    QVariant defaultValue( Qgis::Aggregate aggregate ) const;
};
 
#endif //QGSAGGREGATECALCULATOR_H