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RE: [INTERFACES] Transaction support in 6.5.3/JDBC

From: Peter Mount <petermount(at)it(dot)maidstone(dot)gov(dot)uk>
To: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Assaf Arkin <arkin(at)exoffice(dot)com>
Cc: Peter Mount <petermount(at)it(dot)maidstone(dot)gov(dot)uk>, pgsql-interfaces(at)hub(dot)org
Subject: RE: [INTERFACES] Transaction support in 6.5.3/JDBC
Date: 1999-12-09 07:39:27
Message-ID: 1B3D5E532D18D311861A00600865478C70BF34@exchange1.nt.maidstone.gov.uk (view raw or flat)
Thread:
Lists: pgsql-interfaces
JDBC should break out of the deadlock in the same way as psql. I'll run
some tests, as it might be that the protected method ExecSQL() is
waiting for a normal response, and is ignoring the notify. That's the
only place I can think it is hanging.

Peter

-- 
Peter Mount
Enterprise Support
Maidstone Borough Council
Any views stated are my own, and not those of Maidstone Borough Council.



-----Original Message-----
From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
Sent: Thursday, December 09, 1999 1:01 AM
To: Assaf Arkin
Cc: Peter Mount; pgsql-interfaces(at)hub(dot)org
Subject: Re: [INTERFACES] Transaction support in 6.5.3/JDBC 


Assaf Arkin <arkin(at)exoffice(dot)com> writes:
> I have a very simple test. I start two threads, both of them attempt
to
> do an update on the exact same row in the table, both connections keep
> hanging.

Hmm.  The backend doesn't have any trouble detecting this; I checked
both current sources and 6.5.3:

play=> select * from z1;
f1
--
 1
 2
(2 rows)

play=> begin;
BEGIN
play=> update z1 set f1 = 3 where f1 = 1;
UPDATE 1

<now in a second psql do>

play=> begin;
BEGIN
play=> update z1 set f1 = 4 where f1 = 2;
UPDATE 1
play=> update z1 set f1 = 3 where f1 = 1;

<second psql is now waiting for first one to commit or abort>

<back in first psql do>

play=> update z1 set f1 = 4 where f1 = 2;

After a second or so, one psql will say
NOTICE:  Deadlock detected -- See the lock(l) manual page for a possible
cause.
ERROR:  WaitOnLock: error on wakeup - Aborting this transaction
and the other will say
UPDATE 1

If you're not getting this behavior, then either your test code is wrong
or there's something broken in the JDBC driver...

			regards, tom lane

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Next:From: martenDate: 1999-12-09 08:00:09
Subject: Re: [INTERFACES] locking on database updates
Previous:From: Peter MountDate: 1999-12-09 07:28:11
Subject: RE: [INTERFACES] Transaction support in 6.5.3/JDBC

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