[Interest] QSqlDatabase and threads

Karl Ruetz karl.ruetz at ruetzdogz.com
Thu May 30 18:31:10 CEST 2013


Both the documentation and my own experience say what you are after
is not possible:


I do a similar thing only with MySQL. I am forced to create a
QSqlDatabase object with each thread. If I do not, I get dead locked
situations once in awhile. With Sqlite, I would think there would be
some I/O conflicts since the database is actually a file. 

A connection
per thread seems the only safe way to approach it. 


2013-05-30 10:03, Witold E Wolski wrote: 

> I am using threading to
speed up compuation. Each thread produces some results which I would
like to store in a sqlite file. 
> My idea is to have something like
an monitor object which has an QSqlDatabase member and a insert method
which is synchronized using a mutex. 
> The problem I am actually
running into is that the QSqlDatabase member gets ??? once the pointer
to the Monitor object is passed into to the threads.
> when asked in
the thread it claims to be isOpen and to be isValid but all the inserts
on it fail with 
> insert Feature: Parameter count mismatch 
> On
the other hand if I construct the same object within the thread than
everything works fine. 
> So the instert statements are definitely
> Any ideas ? by the way I am using the tbb for threading.

> Witold 
> _______________________________________________
Interest mailing list
> Interest at qt-project.org
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