Re: My ODBC concurrent Queries

Sorry I forwarded this response only to Martin,
And I have found a resolution to the above problem with Threading =0/1/2,
but I am facing other problems related to connection pooling.

I am following up with that issue on the other thread, hopefully I will find
the resolution soon,

Once again I apologize for not closing down this thread.

Regards,
Jay



---------- Forwarded message ----------
From: J Jayavasanthan <[email protected]>
Date: Tue, May 26, 2009 at 5:42 PM
Subject: Re: My ODBC concurrent Queries
To: Martin Evans <[email protected]>


I think this resolves my query,

Thanks Martin, Thanks for your inputs
Regards,
Jay


On Tue, May 26, 2009 at 1:08 PM, Martin Evans <[email protected]>wrote:

> J Jayavasanthan wrote:
> > Hi Armin,
> > No, the n threads use different connections,
> >
> > And Yes, the codebase is the same for Windows & Linux.
> >
> > BTW, additional information, from windows client connecting Windows &
> Linux
> > MySQL Servers, this problem doesn't arise. But only with Linux clients
> > connecting to Windows or Linux MySQL Servers, this problem arises,
> >
> > I am trying to prepare a testcase out of this, and will put it up
> shortly,
> > do let me know if I have missed something,
> >
> > Regards,
> > Jay
> >
> >
> > 2009/5/25 Armin Schöffmann <[email protected]>
> >
> >> Hi,
> >> tell us a few more implementation details on your app:
> >> In particular, do your n threads share one common db-connection?
> >> Do you use the same codebase for win & linux?
> >>
> >> armin.
> >>
> >>
> >>> -----Original Message-----
> >>> From: J Jayavasanthan [mailto:[email protected]]
> >>> Sent: Monday, May 25, 2009 12:50 PM
> >>> To: [email protected]
> >>> Subject: My ODBC concurrent Queries
> >>>
> >>> Hi,
> >>> In my application, the mysql server is connected via ODBC and we run
> >>> multiple threads executing multiple queries with the mysql server.
> >>> There is
> >>> an issue in our application when we execute a bulk query (more than
> >>> 100,000
> >>> rows in resultset) and when the query takes a longer time for execute,
> >>> all
> >>> the other threads seem to just hang on their db operations.
> >>>
> >>> We are even unable to get past the 'use database' query in most cases
> >>> from
> >>> other threads. Is this a limitation on the ODBC implementation in linux
> >>> or
> >>> have we failed to turn-on any options while building our ODBC drivers,
> >>> do
> >>> let us know.
> >>>
> >>> In Windows, we are able to execute simultaneous queries using ODBC.
> >>> This
> >>> test environment uses all pre-compiled binaries from MySQL website.
> >>>
> >>> In Linux, we are facing the above issues
> >>>
> >>> Linux Flavor - Cent OS 5.2
> >>> MySQL Server version - 5.1.30
> >>> unixODBC version - 2.2.11
> >>> myODBC version - 3.51.27
> >>>
> >>> All Linux binaries are compiled in the same system as they are running.
> >>>
> >>> When we execute two queries as separate processes (same executable
> >>> started
> >>> as different processes), we are able to do so. But, when we create two
> >>> separate threads within the same process, then the above hang up
> >>> arises. Is
> >>> there any particular option in building our application we have missed,
> >>> do
> >>> let us know,
> >>>
> >>> Regards,
> >>> Jayavasanthan J
> >
> >
> >
>
> Have you examined the threading options in unixODBC? i.e.,
>
> Threading               = N
>
> for a driver in your odbcinst.ini file. You can read the possible values
> from one of the source modules for unixODBC - I think it is _handles.c.
>
> If the mysql ODBC driver is thread-safe then you can set Threading = 0
> and unixODBC will do nothing to protect the ODBC driver but I cannot
> remember right now what it defaults to - probably 1 or 2 for environment
> or connection.
>
> Also, you might want to look at whether you share the same environment
> between threads even if they are using different connections (see
> SQLAllocHandle for an environment).
>
> Martin
> --
> Martin J. Evans
> Easysoft Limited
> http://www.easysoft.com
>
>


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