Re: Threads With Libpq

Hi All ..

It seems Semaphores satisfied my conditions ... Below is the modified
behaviour ...

Connection_To_PG()
{
/* Making a connection to PG 9.0 */
}

void* Independent_Thread1()
{
while(1)
{
sleep(5);
/* Doing 1 Insert Operation on Table A*/
*sem_post(&Flag);*
}
}

void* Independent_Thread2()
{
while(1)
{**
sleep(5);
*sem_wait(&Flag);*
/*Doing 1 Insert Operation on Table B*/
}

main()
{
pthread Ind1,Ind2;
Connection_TO_PG();
pthread_create(&Ind1,NULL,&Independent_Thread1,NULL);
pthread_create(&Ind2,NULL,&Independent_Thread2,NULL);
if(pthread_join(Ind1,NULL)<0)
{
printf("Ind1 is completed");
}
if(pthread_join(Ind2,NULL)<0)
{
printf("Ind2 is completed");
}
}

Thank you all for the wonderful guidance on this ...

Best Regards,
Dinesh
manojadinesh.blogspot.com

On Wed, Aug 1, 2012 at 8:34 PM, dinesh kumar <dineshkumar02(at)gmail(dot)com>wrote:

> Hi Merlin/Alban,
>
> Thank you very much for your guidance .. Sure will use Async Llibpq
> Functionalities or Will use Thread Mutex for making the the queries to be
> synchronize ...
>
> Best Regards,
> Dinesh
> manojadinesh.blogspot.com
>
>
> On Wed, Aug 1, 2012 at 7:33 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>
>> On Wed, Aug 1, 2012 at 8:09 AM, Alban Hertroys <haramrae(at)gmail(dot)com>
>> wrote:
>> > On 1 Aug 2012, at 14:32, dinesh kumar wrote:
>> >
>> >> Respected All,
>> >>
>> >> This is my first request/post in PG-Generals. If it is not the place
>> for these kind of queries, then please guide me where i need to be.
>> >>
>> >> I have a quick question regarding "pthread" with PostgreSQL 9.0 Libpq.
>> I'm facing a problem with "Pthread" and libpq. Please find the below
>> program behavoiur.
>> >>
>> >> Connection_To_PG()
>> >> {
>> >> /* Making a connection to PG 9.0 */
>> >> }
>> >>
>> >> void* Independent_Thread1()
>> >> {
>> >> while(1)
>> >> {
>> >> sleep(5);
>> >> /* Doing 1 Insert Operation on Table A*/
>> >> }
>> >> }
>> >>
>> >> void* Independent_Thread2()
>> >> {
>> >> while(1)
>> >> {
>> >> sleep(5);
>> >> /*Doing 1 Insert Operation on Table B*/
>> >> }
>> >>
>> >> main()
>> >> {
>> >> pthread Ind1,Ind2;
>> >> Connection_TO_PG();
>> >> pthread_create(&Ind1,NULL,&Independent_Thread1,NULL);
>> >> pthread_create(&Ind2,NULL,&Independent_Thread2,NULL);
>> >> if(pthread_join(Ind1,NULL)<0)
>> >> {
>> >> printf("Ind1 is completed");
>> >> }
>> >> if(pthread_join(Ind2,NULL)<0)
>> >> {
>> >> printf("Ind2 is completed");
>> >> }
>> >> }
>> >
>> > You need a separate connection per thread or you need to synchronise
>> your queries onto the single central connection, meaning that other threads
>> need to be blocked (from performing queries) while any thread is performing
>> a query.
>> >
>> > Alban Hertroys
>> >
>> > --
>> > Screwing up is an excellent way to attach something to the ceiling.
>>
>> Yeah. Also, OP left out the most important detail, namely where and
>> how the connection object stored. If the objective is to try and make
>> two concurrent actions on the database, I'd consider giving
>> asynchronous queries a whirl:
>> http://www.postgresql.org/docs/8.1/static/libpq-async.html. Basically
>> you pair a PQsendQuery with a PQgetResult. It's a lot easier to code
>> than multi-threaded libpq and tends to be more robust in my
>> experience. If you must use threads, you'll want to keep a connection
>> with each thread instance -- I'd avoid any temptation to use a client
>> side connection pool.
>>
>> merlin
>>
>
>