[PyQt] QSql lastError() must be called BEFORE exec_() ??

[Mario Daniel Carugno]

2009/9/5 Andreas Pakulat <apaku at gmx.de>:
> On 04.09.09 17:23:32, Mario Daniel Carugno wrote:
>> Hi list, i'm coding my first PyQt4-Sql application, and i can't
>> understand a strange behavior.
>> I'll write a snippet of code with an erroneous Sql syntax, and i hope
>> then to catch the error
>> text and display it, in order to know what happened:
>>
>> query = QSqlQuery()
>> query.prepare("insert inta table (name) values ('myname')")  # note
>> that 'inta' is an error
>> query.exec_()
>> if query.isActive() == False:
>>    print "ERRSQL " + str(g_session.db.lastError().text())
>>
>> And this do not work ! It is not displaying any text.
>> To get it work, i must get the error string BEFORE the execution of the query !!
>>
>> query = QSqlQuery()
>> query.prepare("insert inta table (name) values ('myname')")  # i made
>> an erroneous sql
>> query.exec_()
>> errorstr = str(query.lastError().text())
>> if query.isActive() == False:
>>    print "ERRSQL " + errorstr
>>
>> Is that behavior normal ??
>
> Yes.
>
>> How can PyQt get the error's text BEFORE executing the sql statement ?
>
> It doesn't. The errors is fetched _after_ executing the sql statement
> because you're executing the sql statement in the line that calls
> exec_(). If you look at the API docs it pretty clearly states that
> this method executes the prepared sql statement.
>
> The reason the error can be fetched at this point already is because
> there's a syntax error in your SQL, thats usually checked very very
> early during statement execution, hence after the exec_() call the error
> is already set.
>
> If you'd have a long-running query (huge resultset from a select) and
> that throws some kind of error way after it was started you'd probably
> get the error only after isActive returns false.
>
So it means that sometimes i must get error strings before exec_() and
sometimes i have to do it after exec_() ?

Thanks