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

[Bill King]

Yeah, again this is an sqlite issue. Sqlite if I remember correctly
won't close the transaction until you release the read lock (ie close
the select query). Its locking semantics are frustrating at the best of
times... ;)

On 11/21/2009 04:06 AM, ext Israel Brewster wrote:
> 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
>>>> <mailto:israel at frontierflying.com>>
>>>> *To:* Jason H <scorp1us at yahoo.com <mailto:scorp1us at yahoo.com>>
>>>> *Cc:* QT Mailing LIST <qt-interest at trolltech.com
>>>> <mailto: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
>>>>> <mailto:israel at frontierflying.com>>
>>>>> *To:* QT Mailing LIST <qt-interest at trolltech.com
>>>>> <mailto: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 <mailto: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 <mailto: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
> -----------------------------------------------
>


-- 
Bill King, Software Engineer
Qt Development Frameworks, Nokia Pty Ltd
Brisbane Office

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