QSqlQuery Postgres and timestamp => QDateTime(Invalid)

[HenningF]

Hi,

During migration of a project from Qt 6.7.3 to 6.8 I stumbled over a wired invalid QDateTime variant. I can reproduce the bug(?) with a sample project.

The PostgreSQL 16.4 table looks like:

create table test(id serial, tm timestamptz);

I inserted a few rows with now() as timestamp, a select works fine:

testdb=# select * from test;
 id |              tm
----+-------------------------------
  1 | 2024-10-12 08:56:00.330157+02
  2 | 2024-10-12 08:56:03.243138+02
  3 | 2024-10-12 08:56:04.754017+02
(3 rows)

Querying this table with a QSqlQuery object under 6.7.3 shows the expected behavior:

true
QVariant(int, 1) QVariant(QDateTime, QDateTime(2024-10-12 08:56:00.330 Mitteleuropõische Sommerzeit Qt::LocalTime))
QVariant(int, 2) QVariant(QDateTime, QDateTime(2024-10-12 08:56:03.243 Mitteleuropõische Sommerzeit Qt::LocalTime))
QVariant(int, 3) QVariant(QDateTime, QDateTime(2024-10-12 08:56:04.754 Mitteleuropõische Sommerzeit Qt::LocalTime))

Just recompile with Qt 6.8 and the result looks like:

true
QVariant(int, 1) QVariant(QDateTime, QDateTime(Invalid))
QVariant(int, 2) QVariant(QDateTime, QDateTime(Invalid))
QVariant(int, 3) QVariant(QDateTime, QDateTime(Invalid))

So I cannot access timestamp values anymore. Date values are working fine, simple time field not tested.

Am I doing something wrong, missing to send any additional connection parameter or is it simple a bug?

BR Henning

int main(int argc, char* argv[])
{
  QCoreApplication a(argc, argv);

  auto db = QSqlDatabase::addDatabase("QPSQL");
  db.setHostName("loggix");
  db.setDatabaseName("testdb");

  qDebug() << db.open();

  auto query = QSqlQuery(db);

  if (!query.exec("select * from test"))
  {
    qDebug() << db.lastError().text();
    return 1;
  }

  while (query.next())
  {
    qDebug() << query.value("id") << query.value("tm");
  }

  return 0;
}

[HenningF]

I filed a bug report and it seems that the bug is identified and solved.
Mni tnx,

BR Henning

[ChrisW67]

In the Qt 6.8 announcement was this note, "The PostgreSQL and MySQL/MariaDB drivers now correctly handle date and time data when the server is in a different time zone than the client." So, something changed, perhaps not for the better.

[HenningF]

@ChrisW67 Yes, I saw that es well, but I guess, some further info is missing here?

[ChrisW67]

Possibility that QTBUG-115960 and the associated fix have something to do with this. I cannot quite see it though, and I do not have PostgreSql readily to hand. @Christian-Ehrlicher has his name in the bug commentary; perhaps we will get some further comment.

[Christian Ehrlicher]

I'll take a look on it, thx for the report. Please create a bug report.

[HenningF]

I filed a bug report and it seems that the bug is identified and solved.
Mni tnx,

BR Henning