Prepare can fail if the db is not open, or if the statement has problems that can be found during the compilation of the command. Usually they are static, so I often only check the results in a debug build, not a release one.
For SQLLite, I have often found improperly setup file based databases, often return "no connection" or "unable to fetch" for a multitude of issues Scott -----Original Message----- From: Alexander Dyagilev [mailto:alervd...@gmail.com] Sent: Thursday, January 14, 2021 08:41 To: Scott Bloom <sc...@towel42.com>; interest@qt-project.org Subject: Re: [Interest] SQLite: mystic bug: No query Unable to fetch row error On 1/14/2021 7:06 PM, Scott Bloom wrote: > Did the prepare fail? No. But why should it fail? > Do you check to see that the "m_db" database is valid, open, and connected? No. However it should be opened. Anyway, in these cases the error should be different, isn't it? > > Scott > > -----Original Message----- > From: Interest [mailto:interest-boun...@qt-project.org] On Behalf Of > Alexander Dyagilev > Sent: Thursday, January 14, 2021 07:19 > To: interest@qt-project.org > Subject: [Interest] SQLite: mystic bug: No query Unable to fetch row error > > Hello, > > Each instance of our app is supposed to have an unique id (UUID). > > At every start, it check if it has assigned one, and if not - generates it > and saves it to the SQLite database. > > We've found, that 4% of ours users has empty UUIDs. > > We've added some diagnostic reporting info and found, that this is caused by > SQLite database not being able to write generated UUID to it. > > QSqlQuery::exec returns false and its last error returns this error "No query > Unable to fetch row error". > > How can this be? I could not find any problems working with the database in > our code. > > We do it so: > > 1. Make sure the table exists: > > "CREATE TABLE IF NOT EXISTS miscData (Name TEXT, Value BLOB, PRIMARY KEY > (Name))" > > 2. Write value to the table: > > QSqlQuery query(m_db); > query.prepare("REPLACE INTO miscData (Name, Value) VALUES (:Name, :Value)"); > query.bindValue(":Name", "UUID"); query.bindValue(":Value", UuidByteArray); > > if (!query.exec()) > { > // here we're getting this error.... > } > > What are the possible reasons of this error? > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > https://lists.qt-project.org/listinfo/interest _______________________________________________ Interest mailing list Interest@qt-project.org https://lists.qt-project.org/listinfo/interest
