/******************************************************************************** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.**** This file is part of the QtSql module of the Qt Toolkit.**** This file may be used under the terms of the GNU General Public** License version 2.0 as published by the Free Software Foundation** and appearing in the file LICENSE.GPL included in the packaging of** this file.  Please review the following information to ensure GNU** General Public Licensing requirements will be met:** http://www.trolltech.com/products/qt/opensource.html**** If you are unsure which license is appropriate for your use, please** review the following information:** http://www.trolltech.com/products/qt/licensing.html or contact the** sales department at sales@trolltech.com.**** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.******************************************************************************/#include "qsqlrelationaltablemodel.h"#include "qhash.h"#include "qstringlist.h"#include "qsqldatabase.h"#include "qsqldriver.h"#include "qsqlerror.h"#include "qsqlfield.h"#include "qsqlindex.h"#include "qsqlquery.h"#include "qsqlrecord.h"#include "qsqltablemodel_p.h"#include "qdebug.h"/*!    \class QSqlRelation    \brief The QSqlRelation class stores information about an SQL foreign key.    QSqlRelation is a helper class for QSqlRelationalTableModel. See    QSqlRelationalTableModel::setRelation() and    QSqlRelationalTableModel::relation() for details.    \sa QSqlRelationalTableModel, QSqlRelationalDelegate,        {Relational Table Model Example}*//*!    \fn QSqlRelation::QSqlRelation()    Constructs an invalid QSqlRelation object.    For such an object, the tableName(), indexColumn(), and    displayColumn() functions return an empty string.    \sa isValid()*//*!    \fn QSqlRelation::QSqlRelation(const QString &tableName, const QString &indexColumn,                                   const QString &displayColumn)    Constructs a QSqlRelation object, where \a tableName is the SQL    table name to which a foreign key refers, \a indexColumn is the    foreign key, and \a displayColumn is the field that should be    presented to the user.    \sa tableName(), indexColumn(), displayColumn()*//*!    \fn QString QSqlRelation::tableName() const    Returns the name of the table to which a foreign key refers.*//*!    \fn QString QSqlRelation::indexColumn() const    Returns the index column from table tableName() to which a    foreign key refers.*//*!    \fn QString QSqlRelation::displayColumn() const    Returns the column from table tableName() that should be    presented to the user instead of a foreign key.*//*!    \fn bool QSqlRelation::isValid() const    Returns true if the QSqlRelation object is valid; otherwise    returns false.*/struct QRelation{    QRelation(): model(0) {}    QSqlRelation rel;    QSqlTableModel *model;    QHash<int, QVariant> displayValues;};class QSqlRelationalTableModelPrivate: public QSqlTableModelPrivate{    Q_DECLARE_PUBLIC(QSqlRelationalTableModel)public:    QSqlRelationalTableModelPrivate()        : QSqlTableModelPrivate()    {}    QString escapedRelationField(const QString &tableName, const QString &fieldName) const;    int nameToIndex(const QString &name) const;    mutable QVector<QRelation> relations;    QSqlRecord baseRec; // the record without relations    void clearChanges();    void clearEditBuffer();    void revertCachedRow(int row);    void translateFieldNames(int row, QSqlRecord &values) const;};static void qAppendWhereClause(QString &query, const QString &clause1, const QString &clause2){    if (clause1.isEmpty() && clause2.isEmpty())        return;    if (clause1.isEmpty() || clause2.isEmpty())        query.append(QLatin1String(" WHERE (")).append(clause1).append(clause2);    else        query.append(QLatin1String(" WHERE (")).append(clause1).append(                        QLatin1String(") AND (")).append(clause2);    query.append(QLatin1String(") "));}void QSqlRelationalTableModelPrivate::clearChanges(){    for (int i = 0; i < relations.count(); ++i) {        QRelation &rel = relations[i];        delete rel.model;        rel.displayValues.clear();    }}void QSqlRelationalTableModelPrivate::revertCachedRow(int row){    if (cache.value(row).op == QSqlTableModelPrivate::Insert) {        for (int i = 0; i < relations.count(); ++i) {            const QHash<int, QVariant> displayValues = relations.at(i).displayValues;            QHash<int, QVariant> newValues;            for (QHash<int, QVariant>::const_iterator it = displayValues.constBegin();                 it != displayValues.constEnd(); ++it) {                newValues[it.key() > row ? it.key() - 1 : it.key()] = it.value();            }            relations[i].displayValues = newValues;        }    }    QSqlTableModelPrivate::revertCachedRow(row);}int QSqlRelationalTableModelPrivate::nameToIndex(const QString &name) const{    return baseRec.indexOf(name);}void QSqlRelationalTableModelPrivate::clearEditBuffer(){    editBuffer = baseRec;}/*!    \class QSqlRelationalTableModel    \brief The QSqlRelationalTableModel class provides an editable    data model for a single database table, with foreign key support.    \ingroup database    \module sql    QSqlRelationalTableModel acts like QSqlTableModel, but allows    columns to be set as foreign keys into other database tables.    \table    \row \o \inlineimage noforeignkeys.png         \o \inlineimage foreignkeys.png    \endtable    The screenshot on the left shows a plain QSqlTableModel in a    QTableView. Foreign keys (\c city and \c country) aren't resolved    to human-readable values. The screenshot on the right shows a    QSqlRelationalTableModel, with foreign keys resolved into    human-readable text strings.    The following code snippet shows how the QSqlRelationalTableModel    was set up:    \quotefromfile sql/relationaltablemodel/relationaltablemodel.cpp    \skipto model->setTable    \printline model->setTable    \skipto setRelation    \printline setRelation    \printline setRelation    The setRelation() function calls establish a relationship between    two tables. The first call specifies that column 2 in table \c    employee is a foreign key that maps with field \c id of table \c    city, and that the view should present the \c{city}'s \c name    field to the user. The second call does something similar with    column 3.    If you use a read-write QSqlRelationalTableModel, you probably    want to use QSqlRelationalDelegate on the view. Unlike the default    delegate, QSqlRelationalDelegate provides a combobox for fields    that are foreign keys into other tables. To use the class, simply    call QAbstractItemView::setItemDelegate() on the view with an    instance of QSqlRelationalDelegate:    \quotefromfile sql/relationaltablemodel/relationaltablemodel.cpp    \skipto QTableView *view = new    \printuntil setItemDelegate    The \l{sql/relationaltablemodel} example illustrates how to use    QSqlRelationalTableModel in conjunction with    QSqlRelationalDelegate to provide tables with foreigh key    support.    \image relationaltable.png    Notes:    \list    \o The table's primary key may not contain a relation to       another table.    \o If a relational table contains keys that refer to non-existent       rows in the referenced table, the rows containing the invalid       keys will not be exposed through the model. The user or the       database is responsible for keeping referential integrity.    \endlist    \sa QSqlRelation, QSqlRelationalDelegate,        {Relational Table Model Example}*//*!    Creates an empty QSqlRelationalTableModel and sets the parent to \a parent    and the database connection to \a db. If \a db is not valid, the    default database connection will be used.*/QSqlRelationalTableModel::QSqlRelationalTableModel(QObject *parent, QSqlDatabase db)    : QSqlTableModel(*new QSqlRelationalTableModelPrivate, parent, db){}/*!    Destroys the object and frees any allocated resources.*/QSqlRelationalTableModel::~QSqlRelationalTableModel(){}/*!    \reimp*/QVariant QSqlRelationalTableModel::data(const QModelIndex &index, int role) const{    Q_D(const QSqlRelationalTableModel);    if (role == Qt::DisplayRole && index.column() > 0 && index.column() < d->relations.count()) {        const QVariant v = d->relations.at(index.column()).displayValues.value(index.row());        if (v.isValid())            return v;    }    return QSqlTableModel::data(index, role);}/*!    Sets the data for the \a role in the item with the specified \a    index to the \a value given. Depending on the edit strategy, the