Re: Multi-thread use of a connection

That is what I understood about transactions and a connection and have coded
it to ensure only one transaction is going on a connection. However, but
somebody told me postgres was thread safe and was able handle multiple
transactions on the same connection.

-----Original Message-----
From: pgsql-jdbc-owner@postgresql.org
[mailto:pgsql-jdbc-owner@postgresql.org]On Behalf Of Barry Lind
Sent: Monday, July 22, 2002 7:35 PM
To: cjwhite@cisco.com
Cc: pgsql-jdbc@postgresql.org
Subject: Re: [JDBC] Multi-thread use of a connection




Chris White wrote:

> The documentation states the jdbc driver is thread safe allowing
> multiple threads to share the same connection. The documentation only
> talks about queries. So my question is: What if 2 threads are doing
> transactions and one wants to commit its data, does this mean that the
> other threads data will also be committed even though it hasn't
> completed it's transaction or is the driver aware of this?
>

This is really more of a generic jdbc question and isn't really postgres
specific, but I will attempt to answer.  The postgres jdbc driver should
be thread safe (but I don't believe it has received a lot of testing in
multi-threaded situations so there may be some bugs).  This applies to
both queries and updates.

When it comes to transactions and threads, I think you misunderstand how
jdbc is supposed to work.  The connection defines the scope of the
transaction.  Threads really have nothing to do with transactions.  Thus
if two threads are both using the same connection there is one
transaction (one connection = one transaction).  If either thread ends
the transaction (by calling either commit or rollback on the connection)
it is ended for both threads.  It is for this reason that you generally
don't have multiple threads accessing the same connection because it
becomes very difficult to keep track of the transaction.

thanks,
--Barry



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