qsqlquerymodel.cpp

奇趣公司比较新的qt/emd版本

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#include "qsqlquerymodel.h"

#include <qdebug.h>
#include <qsqldriver.h>
#include <qsqlfield.h>

#include "qsqlquerymodel_p.h"

#define QSQL_PREFETCH 255

void QSqlQueryModelPrivate::prefetch(int limit)
{
    Q_Q(QSqlQueryModel);

    if (atEnd || limit <= bottom.row() || bottom.column() == -1)
        return;

    QModelIndex newBottom;
    const int oldBottomRow = qMax(bottom.row(), 0);

    // try to seek directly
    if (query.seek(limit)) {
        newBottom = q->createIndex(limit, bottom.column());
    } else {
        // have to seek back to our old position for MS Access
        int i = oldBottomRow;
        if (query.seek(i)) {
            while (query.next())
                ++i;
            newBottom = q->createIndex(i, bottom.column());
        } else {
            // empty or invalid query
            newBottom = q->createIndex(-1, bottom.column());
        }
        atEnd = true; // this is the end.
    }
    if (newBottom.row() >= 0 && newBottom.row() > bottom.row()) {
        q->beginInsertRows(QModelIndex(), bottom.row() + 1, newBottom.row());
        bottom = newBottom;
        q->endInsertRows();
    } else {
        bottom = newBottom;
    }
}

QSqlQueryModelPrivate::~QSqlQueryModelPrivate()
{
}

void QSqlQueryModelPrivate::initColOffsets(int size)
{
    colOffsets.resize(size);
    memset(colOffsets.data(), 0, colOffsets.size() * sizeof(int));
}

/*!
    \class QSqlQueryModel
    \brief The QSqlQueryModel class provides a read-only data model for SQL
    result sets.

    \ingroup database
    \module sql

    QSqlQueryModel is a high-level interface for executing SQL
    statements and traversing the result set. It is built on top of
    the lower-level QSqlQuery and can be used to provide data to
    view classes such as QTableView. For example:

    \quotefromfile snippets/sqldatabase/sqldatabase.cpp
    \skipto QSqlQueryModel_snippets
    \skipto QSqlQueryModel *model
    \printuntil show()

    We set the model's query, then we set up the labels displayed in
    the view header.

    QSqlQueryModel can also be used to access a database
    programmatically, without binding it to a view:

    \skipto QSqlQueryModel model;
    \printuntil int salary =

    The code snippet above extracts the \c salary field from record 4 in
    the result set of the query \c{SELECT * from employee}. Assuming
    that \c salary is column 2, we can rewrite the last line as follows:

    \skipto int salary =
    \printline int salary =

    The model is read-only by default. To make it read-write, you
    must subclass it and reimplement setData() and flags(). Another
    option is to use QSqlTableModel, which provides a read-write
    model based on a single database table.

    The \l{sql/querymodel} example illustrates how to use
    QSqlQueryModel to display the result of a query. It also shows
    how to subclass QSqlQueryModel to customize the contents of the
    data before showing it to the user, and how to create a
    read-write model based on QSqlQueryModel.

    If the database doesn't return the amount of selected rows in
    a query, the model will fetch rows incrementally.
    See fetchMore() for more information.

    \sa QSqlTableModel, QSqlRelationalTableModel, QSqlQuery,
        {Model/View Programming}, {Query Model Example}
*/

/*!
    Creates an empty QSqlQueryModel with the given \a parent.
 */
QSqlQueryModel::QSqlQueryModel(QObject *parent)
    : QAbstractTableModel(*new QSqlQueryModelPrivate, parent)
{
}

/*! \internal
 */
QSqlQueryModel::QSqlQueryModel(QSqlQueryModelPrivate &dd, QObject *parent)
    : QAbstractTableModel(dd, parent)
{
}

/*!
    Destroys the object and frees any allocated resources.

    \sa clear()
*/
QSqlQueryModel::~QSqlQueryModel()
{
}

/*!
    \since 4.1

    Fetches more rows from a database.
    This only affects databases that don't report back the size of a query
    (see QSqlDriver::hasFeature()).

    To force fetching of the entire database, you can use the following:

    \code
    while (myModel->canFetchMore())
        myModel->fetchMore();
    \endcode

    \a parent should always be an invalid QModelIndex.

    \sa canFetchMore()
*/
void QSqlQueryModel::fetchMore(const QModelIndex &parent)
{
    Q_D(QSqlQueryModel);
    if (parent.isValid())
        return;
    d->prefetch(qMax(d->bottom.row(), 0) + QSQL_PREFETCH);
}

/*!
    \since 4.1

    Returns true if it is possible to read more rows from the database.
    This only affects databases that don't report back the size of a query
    (see QSqlDriver::hasFeature()).

    \a parent should always be an invalid QModelIndex.

    \sa fetchMore()
 */
bool QSqlQueryModel::canFetchMore(const QModelIndex &parent) const
{
    Q_D(const QSqlQueryModel);
    return (!parent.isValid() && !d->atEnd);
}

/*! \fn int QSqlQueryModel::rowCount(const QModelIndex &parent) const
    \since 4.1

    If the database supports returning the size of a query
    (see QSqlDriver::hasFeature()), the amount of rows of the current
    query is returned. Otherwise, returns the amount of rows
    currently cached on the client.

    \a parent should always be an invalid QModelIndex.

    \sa canFetchMore(), QSqlDriver::hasFeature()
 */
int QSqlQueryModel::rowCount(const QModelIndex &index) const
{
    Q_D(const QSqlQueryModel);
    return index.isValid() ? 0 : d->bottom.row() + 1;
}

/*! \reimp
 */
int QSqlQueryModel::columnCount(const QModelIndex &index) const
{
    Q_D(const QSqlQueryModel);
    return index.isValid() ? 0 : d->rec.count();
}

/*!
    Returns the value for the specified \a item and \a role.

    If \a item is out of bounds or if an error occurred, an invalid
    QVariant is returned.

    \sa lastError()
*/
QVariant QSqlQueryModel::data(const QModelIndex &item, int role) const
{
    Q_D(const QSqlQueryModel);
    if (!item.isValid())
        return QVariant();

    QVariant v;
    if (role & ~(Qt::DisplayRole | Qt::EditRole))
        return v;

    if (!d->rec.isGenerated(item.column()))
        return v;
    QModelIndex dItem = indexInQuery(item);
    if (dItem.row() > d->bottom.row())
        const_cast<QSqlQueryModelPrivate *>(d)->prefetch(dItem.row());

    if (!d->query.seek(dItem.row())) {
        d->error = d->query.lastError();
        return v;
    }

    return d->query.value(dItem.column());
}

/*!
    Returns the header data for the given \a role in the \a section
    of the header with the specified \a orientation.
*/
QVariant QSqlQueryModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    Q_D(const QSqlQueryModel);
    if (orientation == Qt::Horizontal) {
        QVariant val = d->headers.value(section).value(role);
        if (role == Qt::DisplayRole && !val.isValid())
            val = d->headers.value(section).value(Qt::EditRole);
        if (val.isValid())
            return val;
        if (role == Qt::DisplayRole && d->rec.count() > section)
            return d->rec.fieldName(section);
    }
    return QAbstractItemModel::headerData(section, orientation, role);
}

/*!
    This virtual function is called whenever the query changes. The
    default implementation does nothing.

    query() returns the new query.

    \sa query(), setQuery()
 */
void QSqlQueryModel::queryChange()
{
    // do nothing
}