Обсуждение: libpq and multi-threading on Linux?

Hi folks,

I apologize in advance if I have overlooked docs, but I haven't been
able to find a discussion of how PostGreSQL via libpq on Linux fares
with pthreads. Can someone point me to docs if available, or otherwise
enlighten me? How well does it work and what are the important design
issues to consider?

I'm expecting to create a pool of db connections to use within a
long-running process, which will create a new thread for each incoming
request from a client. I've found just a very little bit about PG
being multi-processing, but not how it will interact with a
multi-threaded client. I appreciate your comments.

thanks,
--Michael

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I succeeded in doing exactly that.  I simply took the C source examples on
the Postgres documentation and pasted it into the thread with no problems
at all.  The only changes made to the examples were just simple ones like
return values or fprintf(stderr) stuff, but that's all. Postgres server
and libpq libraries run flawlessly in pthreads.

For me, synchronization was not required since each thread did not share
resources with other threads.  Each thread personally initialized the
libpq connection, did its job and destroyed the connection, just like the
example.

Brendan

Michael Olivier wrote:

> Hi folks,
>
> I apologize in advance if I have overlooked docs, but I haven't been
> able to find a discussion of how PostGreSQL via libpq on Linux fares
> with pthreads. Can someone point me to docs if available, or otherwise
> enlighten me? How well does it work and what are the important design
> issues to consider?
>
> I'm expecting to create a pool of db connections to use within a
> long-running process, which will create a new thread for each incoming
> request from a client. I've found just a very little bit about PG
> being multi-processing, but not how it will interact with a
> multi-threaded client. I appreciate your comments.
>
> thanks,
> --Michael
>
> _________________________________________________________
> DO YOU YAHOO!?
> Get your free @yahoo.com address at http://mail.yahoo.com

On Wed, 10 Feb 1999, Michael Olivier wrote:

> Hi folks,
>
> I apologize in advance if I have overlooked docs, but I haven't been
> able to find a discussion of how PostGreSQL via libpq on Linux fares
> with pthreads. Can someone point me to docs if available, or otherwise
> enlighten me? How well does it work and what are the important design
> issues to consider?
>
> I'm expecting to create a pool of db connections to use within a
> long-running process, which will create a new thread for each incoming
> request from a client. I've found just a very little bit about PG
> being multi-processing, but not how it will interact with a
> multi-threaded client. I appreciate your comments.

Take a look on how I got the JDBC driver to handle multi-threading.

At certain points, the driver obtains a lock on the network connection
before sending a query, and releases the lock when the query has finished
(ie: all results have been returned in to the ResultSet).

Another place where this locking occurs is in FastPath, a lock is obtained
on the network connection before sending the function call, and released
when the call returns.

When another thread tries to run a query, it has to wait until the lock is
released, then it can use that network connection. Also, it allows calls
to LargeObjects to run in one thread without any worries of confusing the
backend while queries are running.

I'm not sure if this is what you were after.

Peter

--
       Peter T Mount peter@retep.org.uk
      Main Homepage: http://www.retep.org.uk
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