/*!
Prepares the SQL query \a query for execution. Returns true if the
query is prepared successfully; otherwise returns false.
The query may contain placeholders for binding values. Both Oracle
style colon-name (e.g., \c{:surname}), and ODBC style (\c{?})
placeholders are supported; but they cannot be mixed in the same
query. See the \l{QSqlQuery examples}{Detailed Description} for
examples.
Portability note: Some databases choose to delay preparing a query
until it is executed the first time. In this case, preparing a
syntactically wrong query succeeds, but every consecutive exec()
will fail.
For SQLite, the query string can contain only one statement at a time.
If more than one statement is given, the function returns false.
Example:
\snippet sqldatabase/sqldatabase.cpp 9
\sa exec(), bindValue(), addBindValue()
*/
bool QSqlQuery::prepare(const QString& query)
{
if (d->ref.load() != 1) {
bool fo = isForwardOnly();
*this = QSqlQuery(driver()->createResult());
setForwardOnly(fo);
d->sqlResult->setNumericalPrecisionPolicy(d->sqlResult->numericalPrecisionPolicy());
} else {
d->sqlResult->setActive(false);
d->sqlResult->setLastError(QSqlError());
d->sqlResult->setAt(QSql::BeforeFirstRow);
d->sqlResult->setNumericalPrecisionPolicy(d->sqlResult->numericalPrecisionPolicy());
}
if (!driver()) {
qWarning("QSqlQuery::prepare: no driver");
return false;
}
if (!driver()->isOpen() || driver()->isOpenError()) {
qWarning("QSqlQuery::prepare: database not open");
return false;
}
if (query.isEmpty()) {
qWarning("QSqlQuery::prepare: empty query");
return false;
}
#ifdef QT_DEBUG_SQL
qDebug("\n QSqlQuery::prepare: %s", query.toLocal8Bit().constData());
#endif
return d->sqlResult->savePrepare(query);
}
bool QSqlQuery::exec(const QString& query)
{
#ifdef QT_DEBUG_SQL
QElapsedTimer t;
t.start();
#endif
if (d->ref.load() != 1) {
bool fo = isForwardOnly();
*this = QSqlQuery(driver()->createResult());
d->sqlResult->setNumericalPrecisionPolicy(d->sqlResult->numericalPrecisionPolicy());
setForwardOnly(fo);
} else {
d->sqlResult->clear();
d->sqlResult->setActive(false);
d->sqlResult->setLastError(QSqlError());
d->sqlResult->setAt(QSql::BeforeFirstRow);
d->sqlResult->setNumericalPrecisionPolicy(d->sqlResult->numericalPrecisionPolicy());
}
d->sqlResult->setQuery(query.trimmed());
if (!driver()->isOpen() || driver()->isOpenError()) {
qWarning("QSqlQuery::exec: database not open");
return false;
}
if (query.isEmpty()) {
qWarning("QSqlQuery::exec: empty query");
return false;
}
bool retval = d->sqlResult->reset(query);
#ifdef QT_DEBUG_SQL
qDebug().nospace() << "Executed query (" << t.elapsed() << "ms, " << d->sqlResult->size()
<< " results, " << d->sqlResult->numRowsAffected()
<< " affected): " << d->sqlResult->lastQuery();
#endif
return retval;
}
bool MSqlQuery::prepare(const QString& query)
{
if (!m_db)
{
// Database structure's been deleted
return false;
}
m_last_prepared_query = query;
#ifdef DEBUG_QT4_PORT
if (query.contains(m_testbindings))
{
LOG(VB_GENERAL, LOG_DEBUG,
QString("\n\nQuery contains bind value \"%1\" twice:\n\n\n")
.arg(m_testbindings.cap(1)) + query);
#if 0
exit(1);
#endif
}
#endif
// Database connection down. Try to restart it, give up if it's still
// down
if (!m_db)
{
// Database structure has been deleted...
return false;
}
if (!m_db->isOpen() && !Reconnect())
{
LOG(VB_GENERAL, LOG_INFO, "MySQL server disconnected");
return false;
}
// QT docs indicate that there are significant speed ups and a reduction
// in memory usage by enabling forward-only cursors
//
// Unconditionally enable this since all existing uses of the database
// iterate forward over the result set.
setForwardOnly(true);
bool ok = QSqlQuery::prepare(query);
// if the prepare failed with "MySQL server has gone away"
// Close and reopen the database connection and retry the query if it
// connects again
if (!ok && QSqlQuery::lastError().number() == 2006 && Reconnect())
ok = true;
if (!ok && !(GetMythDB()->SuppressDBMessages()))
{
LOG(VB_GENERAL, LOG_ERR,
QString("Error preparing query: %1").arg(query));
LOG(VB_GENERAL, LOG_ERR,
MythDB::DBErrorMessage(QSqlQuery::lastError()));
}
return ok;
}
