"database table is locked Unable to fetch row"

Chrisw01

Hello, I seem to be having issues with QSql.

I am using QT 5.7 with mingw 32 compiler. When I try to drop a database table sql.exec() Return false and I receive the following error in lastError()->text(); "database table is locked Unable to fetch row".

My SQL to delete the table is

bool result = sql.exec("drop table SYSTEM_PROPERTIES"); // Always returns false and sets the above error.

I can execute the above sql statement in a database manager without failure however.

Thanks for any light you can shed on the matter.

Chris--

SGaist

Hi,

How many threads do you have in your application ?

Chrisw01

Hi, not creating any threads so I assume the answer is just the main one.

Thanks

SGaist

Any pending request on that table ?

Chrisw01

@SGaist None that I know of, in fact I can make that the first call right after the database is opened and it fails. I am going to install the latest version of QT and see if the problem goes away. I'll post the results when this is completed.

Thanks..

SGaist

What backend are you using ? MySQL, PostgreSQL ? SQLite ?

Chrisw01

MySQL, but I found the problem, in my code I call select * from a database but I only wanted to get the first entry of the database so instead of letting the sql statement finish with a while(sql.next()) I called if(sql.next()) then processed my data thus not allowing sql to finish. As soon as I added sql.finish() my problem went away. What I don't understand is the select I was calling was on a different table than the one I Was trying to work with.

Anyways, I'm in the process of updating all of my code to call sql.finish() on all sql statements.

Thanks for your help on this.

SGaist

If you only want the first entry, why not use the LIMIT keyword with your query ? That way to don't have to resort to workaround like you are doing.

Chrisw01

That's a good idea, thanks.