QSqlQuery and seek() - doesn't work on first call.

[amicitas]

I am trying to use the QSqlQuery.seek() function. I am running into a problem in which the first time that I call seek after a query it doesn't seem to do anything. If I call it a second time it does what I would expect. If I call next() before seek() it also behaves as expected. What is going on here?

I am using the SQLite database for this and programing in PyQt4.

Example Code:

print 'is_active', self.query.isActive()
        print 'is_select', self.query.isSelect()
        print 'is_valid', self.query.isValid()
 
        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()
 
        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()
 
        print ''
        print 'next', self.query.next()
        print 'is_valid', self.query.isValid()
 
        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()

print 'is_active', self.query.isActive()
        print 'is_select', self.query.isSelect()
        print 'is_valid', self.query.isValid()

        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()

        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()

        print ''
        print 'next', self.query.next()
        print 'is_valid', self.query.isValid()

        print ''
        print 'seek:', self.query.seek(0)
        print 'is_valid', self.query.isValid()

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Result:

is_active True
is_select True
is_valid False
 
seek: False
is_valid False
 
seek: True
is_valid True
 
next False
is_valid False
 
seek: True
is_valid True

is_active True
is_select True
is_valid False

seek: False
is_valid False

seek: True
is_valid True

next False
is_valid False

seek: True
is_valid True

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Thanks for any help with this,

amicitas

[yuriry]

I tested your code on PostgreSQL using C++ and got correct results (I used a query that returns a single record, looks like you did the same). May be there is a bug in SqlLite driver or in PyQt4?

Test program

int main(int argc, char* argv[])
{
  QCoreApplication app(argc, argv);
 
  QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
  db.setDatabaseName("pm");
 
  bool ok = db.open();
  if(! ok) {
    qDebug() << db.lastError().text();
    return 1;
  }
 
  QSqlQuery query;
  if(query.exec("select * from pm.portfolio where id = 1")) {
    qDebug() <<  "is_active" << query.isActive();
    qDebug() <<  "is_select" << query.isSelect();
    qDebug() <<  "is_valid" << query.isValid();
 
    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();
 
    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();
 
    qDebug() <<  "";
    qDebug() <<  "next" << query.next();
    qDebug() <<  "is_valid" << query.isValid();
 
    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();
  }
  else {
    qDebug() << query.lastError();
  }
}

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

  QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
  db.setDatabaseName("pm");

  bool ok = db.open();
  if(! ok) {
    qDebug() << db.lastError().text();
    return 1;
  }

  QSqlQuery query;
  if(query.exec("select * from pm.portfolio where id = 1")) {
    qDebug() <<  "is_active" << query.isActive();
    qDebug() <<  "is_select" << query.isSelect();
    qDebug() <<  "is_valid" << query.isValid();

    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();

    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();

    qDebug() <<  "";
    qDebug() <<  "next" << query.next();
    qDebug() <<  "is_valid" << query.isValid();

    qDebug() <<  "";
    qDebug() <<  "seek:" << query.seek(0);
    qDebug() <<  "is_valid" << query.isValid();
  }
  else {
    qDebug() << query.lastError();
  }
}

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Result

is_active true
is_select true
is_valid false

seek: true
is_valid true

seek: true
is_valid true

next false
is_valid false

seek: true
is_valid true