[Qt-interest] [SOLVED] QSqlQuery caching INSERT data?

Fri Nov 20 19:06:53 CET 2009

On Nov 20, 2009, at 8:44 AM, Israel Brewster wrote:

>
> On Nov 20, 2009, at 7:57 AM, Israel Brewster wrote:
>
>>
>> On Nov 19, 2009, at 2:59 PM, Jason H wrote:
>>
>>> I haven't seen this for some time...
>>>
>>> I wonder what Qt version / QSqlDriver version you have. Autocommit  
>>> I think is on by default these days...
>>>
>>
>> Yeah, I probably should have mentioned that. Qt 4.5.3, with  
>> whatever version of the QSqlite driver comes with that. Now that  
>> you mention it, I don't recall seeing this behavior until I  
>> upgraded from 4.5.2 to 4.5.3. Maybe I should try with 4.5.2 again,  
>> and see what happens.
>
> Nope, I was wrong, this happens with 4.5.2 as well. I must just have  
> not noticed it due to the way my code worked before. Guess I'll have  
> to look elsewhere.

Figured it out: the problem was with my code. As stated here: http://doc.trolltech.com/4.5/qsqldatabase.html#commit 
, "For some databases, the commit will fail and return false if there  
is an active query using the database for a SELECT". Which is exactly  
what was happening for me - I had a select statement in the main  
function that wasn't being set inactive until main returned - i.e.  
when I quit the application. It is a little confusing, as the commit()  
function appears to only apply when you are using transactions (which  
I wasn't), but apparently behind the scenes Qt does, even when just  
doing an insert from a QSqlQuery. Or something. Dunno. Either way,  
it's working now. Thanks for the feedback.

>
>>
>>>
>>> From: Israel Brewster <israel at frontierflying.com>
>>> To: Jason H <scorp1us at yahoo.com>
>>> Cc: QT Mailing LIST <qt-interest at trolltech.com>
>>> Sent: Thu, November 19, 2009 6:47:52 PM
>>> Subject: Re: [Qt-interest] QSqlQuery caching INSERT data?
>>>
>>>
>>> On Nov 19, 2009, at 2:44 PM, Jason H wrote:
>>>
>>>> Make sure that you are auto committing transactions, or are  
>>>> manually committing them.
>>>>
>>>> No it does not cache them, but your DB might. I've seen this  
>>>> before, wher SQLite will make a .journal file with the insert  
>>>> content, but won;t be committed because you never commited the  
>>>> transaction. Then, when you run your program again, the .journal  
>>>> is deleted because it doesn't have a completed transaction.
>>>
>>> Thanks. That sounds like exactly what is happening (I am seeing  
>>> the journal file), except that I am not using transactions. I did  
>>> try calling commit(), just for kicks, but it returned false as  
>>> expected.
>>>
>>>>
>>>>
>>>>
>>>> From: Israel Brewster <israel at frontierflying.com>
>>>> To: QT Mailing LIST <qt-interest at trolltech.com>
>>>> Sent: Thu, November 19, 2009 4:04:48 PM
>>>> Subject: [Qt-interest] QSqlQuery caching INSERT data?
>>>>
>>>> Does QSqlQuery do any caching of INSERT statements? If so, is  
>>>> there a way to force the cache to be flushed to the database? I  
>>>> have a program that executes a number of INSERT statements using  
>>>> QSqlQuery, but they don't seem to be written to disk until the  
>>>> app quits. Usually this isn't a problem, and is probably a good  
>>>> thing, but there are a couple of places where this doesn't work  
>>>> for me. I tried using a QSqlDatbase::close() command, but this  
>>>> doesn't seem to produce the desired result. I didn't think  
>>>> QSqlQuery did any caching aside from results, which makes me  
>>>> think this is a SQLite process that doing the caching, but I  
>>>> wanted to ask here anyway. Even if it is SQLite, is there some Qt  
>>>> command I could run to make SQLite think I am done and write the  
>>>> data out? Thanks for any advice!
>>>>
>>>> -----------------------------------------------
>>>> Israel Brewster
>>>> Computer Support Technician II
>>>> Frontier Flying Service Inc.
>>>> 5245 Airport Industrial Rd
>>>> Fairbanks, AK 99709
>>>> (907) 450-7250 x293
>>>> -----------------------------------------------
>>>>
>>>>
>>>>
>>>>
>>>
>>> -----------------------------------------------
>>> Israel Brewster
>>> Computer Support Technician II
>>> Frontier Flying Service Inc.
>>> 5245 Airport Industrial Rd
>>> Fairbanks, AK 99709
>>> (907) 450-7250 x293
>>> -----------------------------------------------
>>>
>>>
>>>
>>>
>>
>> -----------------------------------------------
>> Israel Brewster
>> Computer Support Technician II
>> Frontier Flying Service Inc.
>> 5245 Airport Industrial Rd
>> Fairbanks, AK 99709
>> (907) 450-7250 x293
>> -----------------------------------------------
>>
>> <Israel Brewster.vcf>
>>
>> _______________________________________________
>> Qt-interest mailing list
>> Qt-interest at trolltech.com
>> http://lists.trolltech.com/mailman/listinfo/qt-interest
>
> -----------------------------------------------
> Israel Brewster
> Computer Support Technician II
> Frontier Flying Service Inc.
> 5245 Airport Industrial Rd
> Fairbanks, AK 99709
> (907) 450-7250 x293
> -----------------------------------------------
>
> <Israel Brewster.vcf>
>
> _______________________________________________
> Qt-interest mailing list
> Qt-interest at trolltech.com
> http://lists.trolltech.com/mailman/listinfo/qt-interest

-----------------------------------------------
Israel Brewster
Computer Support Technician II
Frontier Flying Service Inc.
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7250 x293
-----------------------------------------------

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