Re: [sqlite] Database gets locked for other processes

[Israel Lins Albuquerque]

I know well the qt sqlite to say, maybe you aren't destroing the QSqlQuery 
class or simple call finish function, and the statement is openned helding the 
lock!

Enviado via iPhone

> Em 29/10/2013, às 10:51, Stephan Beal  escreveu:
> 
>> On Tue, Oct 29, 2013 at 1:52 PM, Martin  wrote:
>> 
>> The program is running on Windows7.
>> ...
> 
> The program runs parallel on multiple machines all sharing the same
>> SQLite-Database-file.
> 
> 
> Connecting multiple clients over a network share is a sure-fire way to
> corrupt your database. See the bottom half of this page:
> 
> http://www.sqlite.org/whentouse.html
> 
> as well as any number of threads in this mailing list archives regarding
> this topic.
> 
> -- 
> - stephan beal
> http://wanderinghorse.net/home/stephan/
> http://gplus.to/sgbeal
> "Since tyranny's the only guaranteed byproduct of those who insist on a
> perfect world, freedom will have to do." -- Bigby Wolf
> ___
> sqlite-users mailing list
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Re: [sqlite] Database gets locked for other processes

[jose isaias cabrera]

"Martin Kropfinger"

Am Tue, 29 Oct 2013 12:00:02 -0400
schrieb sqlite-users-requ...@sqlite.org:


Date: Tue, 29 Oct 2013 14:51:08 +0100
From: Stephan Beal <sgb...@googlemail.com>
To: General Discussion of SQLite Database <sqlite-users@sqlite.org>
Subject: Re: [sqlite] Database gets locked for other processes
Message-ID:
<cakd4naigijjvwbks7z2-s_v3j+ingts5ugrnft3krjjytex...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

On Tue, Oct 29, 2013 at 1:52 PM, Martin <free...@rakor-net.de> wrote:

> The program is running on Windows7.
> ...

The program runs parallel on multiple machines all sharing the same
> SQLite-Database-file.


Connecting multiple clients over a network share is a sure-fire way to
corrupt your database. See the bottom half of this page:

http://www.sqlite.org/whentouse.html

as well as any number of threads in this mailing list archives
regarding this topic.



I can understand this. But I need to have the database unconnected to a
special sever. In fact it has the same issues if I run more than one
program on the same machine tying to access the same lokal databasefile.


First of all, everything that every one has said here damaging the DB, is 
correct. so, if you want to continue, read on...


I have a system of 10 people that use a program manager tool that uses 
SQLite3 as the main DB using a server shared db.  I have been able to use it 
by putting a block outside of SQLite when someone is writing to the DB. 
What I do is that I have a place in the same server, or even same spot where 
the DB lives,  that a file will be created before someone is going to write 
to the DB.  This file will tell the tool that someone is writing to the DB 
and no one else will be allow to write.  They can read, but not write.  When 
the tool is going to write to the DB, it checks to see if that file is 
there.  If it is, it waits for a few seconds and it checks again until that 
file is deleted. However, this causes the users, sometimes, to complain of 
slow response.  I tell them what is going on, but they still harrass me. 
Anyway, again, doing this could damaged your DB, but if you really need this 
to work, there are ways of working around it.  By the way, before figuring 
this out, I damaged my DB a few times, so you better make sure you have a 
good backup system.  Ihth.


josé 


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Re: [sqlite] Database gets locked for other processes

[Martin Kropfinger]

Am Tue, 29 Oct 2013 12:00:02 -0400
schrieb sqlite-users-requ...@sqlite.org:

> Date: Tue, 29 Oct 2013 14:51:08 +0100
> From: Stephan Beal <sgb...@googlemail.com>
> To: General Discussion of SQLite Database <sqlite-users@sqlite.org>
> Subject: Re: [sqlite] Database gets locked for other processes
> Message-ID:
>   <cakd4naigijjvwbks7z2-s_v3j+ingts5ugrnft3krjjytex...@mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> On Tue, Oct 29, 2013 at 1:52 PM, Martin <free...@rakor-net.de> wrote:
> 
> > The program is running on Windows7.
> > ...  
> 
> The program runs parallel on multiple machines all sharing the same
> > SQLite-Database-file.  
> 
> 
> Connecting multiple clients over a network share is a sure-fire way to
> corrupt your database. See the bottom half of this page:
> 
> http://www.sqlite.org/whentouse.html
> 
> as well as any number of threads in this mailing list archives
> regarding this topic.
> 

I can understand this. But I need to have the database unconnected to a
special sever. In fact it has the same issues if I run more than one
program on the same machine tying to access the same lokal databasefile.

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Re: [sqlite] Database gets locked for other processes

[Stephan Beal]

On Tue, Oct 29, 2013 at 1:52 PM, Martin  wrote:

> The program is running on Windows7.
> ...

The program runs parallel on multiple machines all sharing the same
> SQLite-Database-file.


Connecting multiple clients over a network share is a sure-fire way to
corrupt your database. See the bottom half of this page:

http://www.sqlite.org/whentouse.html

as well as any number of threads in this mailing list archives regarding
this topic.

-- 
- stephan beal
http://wanderinghorse.net/home/stephan/
http://gplus.to/sgbeal
"Since tyranny's the only guaranteed byproduct of those who insist on a
perfect world, freedom will have to do." -- Bigby Wolf
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Re: [sqlite] Database gets locked for other processes

[Richard Hipp]

Sounds like something changed in Qt 5.1.1 so that it is holding open a read
transaction.  The first process acquires the read transaction, which
permits other processes to read but prevents anybody else from writing.  I
have no idea why Qt would do this, though.

You can change to WAL mode, which will allow other processes to write while
the original process holds the read transaction open.  But with the read
transaction active, you'll never be able to checkpoint and so the WAL file
will grow without bound.  Things will appear to work at first, but you will
eventual run into performance problems with a huge WAL file.

I think your goal should be to figure out why Qt 5.1.1 is holding open the
read transaction.


On Tue, Oct 29, 2013 at 8:52 AM, Martin  wrote:

> Hi there!
>
> I have a program written in Qt and using the SQLite-drivers shipped with
> Qt.
> AFAIK those are the original SQLite-drivers. The program is running on
> Windows7.
>
> Originally the program was written using Qt4.8 (which came with SQLite
> 3.7.14.1). The program runs parallel on multiple machines all sharing the
> same
> SQLite-Database-file. The programs have 99% reading access (SELECT). Some
> times
> there will be some data written/changed. All clients may change the data.
> Until now this worked without issues.
>
> Now I am porting the program from Qt 4.8 to Qt 5.1.1 (shipping SQLite
> 3.7.17)
> and am running in trouble with parallel access to the database-file. The
> first
> program accessing the database can work normally with the database. But all
> programs starting
> later can only access the database for reading. If one of them wants to
> write
> data in the database I get a "database-locked-error".
>
> Can you tell me if I am doing something wrong, or if there is a good
> reason for
> this habbit?
>
> All the programs connect to database at startup and close the
> databaseconnection
> on program close.
>
> Thanks for your help
>
> Martin
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-- 
D. Richard Hipp
d...@sqlite.org
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[sqlite] Database gets locked for other processes

[Martin]

Hi there!

I have a program written in Qt and using the SQLite-drivers shipped with Qt.
AFAIK those are the original SQLite-drivers. The program is running on Windows7.

Originally the program was written using Qt4.8 (which came with SQLite
3.7.14.1). The program runs parallel on multiple machines all sharing the same
SQLite-Database-file. The programs have 99% reading access (SELECT). Some times
there will be some data written/changed. All clients may change the data.
Until now this worked without issues.

Now I am porting the program from Qt 4.8 to Qt 5.1.1 (shipping SQLite 3.7.17)
and am running in trouble with parallel access to the database-file. The first
program accessing the database can work normally with the database. But all
programs starting
later can only access the database for reading. If one of them wants to write
data in the database I get a "database-locked-error".

Can you tell me if I am doing something wrong, or if there is a good reason for
this habbit?

All the programs connect to database at startup and close the databaseconnection
on program close.

Thanks for your help

Martin
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