Do not get result for all sqlite pragmas via QSqlQuery - linux

Question

I want to get the current states of sqlite pragma using Qt's QSqlQuery.
But I do not get a result for some values from the program but from sqlite console.
Qt version 5.2.1, Sqlite version 3.8.4.3, Windows 7, Ubuntu 12.4 LTS
Output:
application_id = "0"
auto_vacuum = "0"
automatic_index = "1"
busy_timeout = "5000"
cache_size = "2000"
cache_spill = [NoResult]
case_sensitive_like = [NoResult]
void MySqliteInfo::PrintState(QString state)
{
printf("%s = ", state.toStdString().c_str());
QSqlQuery query(*m_db);
query.prepare(QString("PRAGMA %1").arg(state));
query.exec();
if(0 == query.size()) {
printf("%s returns nothing\n", state.toStdString().c_str());
}
else {
if(query.next()) {
QVariant value = query.value(0);
if(value.canConvert(QMetaType::QString)) {
printf("\"%s\"\n", value.toString().toStdString().c_str());
}
else {
printf("[UnknownDataType]\n");
}
}
else {
printf("[NoResult]\n");
}
}
query.finish();
}
PrintState("application_id");
PrintState("auto_vacuum");
PrintState("automatic_index");
PrintState("busy_timeout");
PrintState("cache_size");
PrintState("cache_spill");
PrintState("case_sensitive_like");

Answer 1

The SQLite version that you are actually using in your Qt program does not yet implement PRAGMA cache_spill.
SQLite just ignores any PRAGMA it does not recognize.
As documented, PRAGMA case_sensitive_like does not allow reading the current value.

Answer 2

First of all, the query.size() test ist useless, since it returns -1 for every value. query.size() can only be used with SELECT queries.
Now [NoResult] can have two different meanings:
A pragma value does not exist
A pragma value is Not Set
In an example database created from another program, I observe the first case for cache_spill and the second case for case_sensitive_like. You might want to check the values using sqliteman on Ubuntu.

Answer 3

I found the solution tt least for cache_spill:
The used sqlite3.exe supports pragma cache_spill but not the sqlite version comes with Qt 5.2. (3.7.17).
Qt 5.3 comes with Sqlite 3.8.4.3 - the git repro says this.