Psycopg; How to detect row locking?

[Cliff Wells]

On Mon, 2004-09-27 at 13:40 +0200, Alban Hertroys wrote:
> Good day,
> 
> I have a number of threads doing inserts in a table, after which I want 
> to do a select. This means that it will occur that the row that I want 
> to select is locked (by the DB). In these cases, I believe I receive an 
> OperationalError (or is it an InterfaceError?).
> 
> Is it possible (and if so - how?) to verify that the exception occured 
> because of row locking, so that I can wait and try again?

I've seen this exception and frankly, it has always occurred due to row
locking.  Simply retry the query until it completes.

> Or are there better ways to achieve this? I'm not too charmed about 
> polling loops that may never end.

I've written multithreaded apps with hundreds of threads that used the
retry technique and never had a problem.  In fact, I believe Zope uses
this method.

> I'm using python 2.3 with psycopg 1.1.13 and PostgreSQL 7.4.2.
> 
> Regards, Alban Hertroys.
-- 
Cliff Wells <clifford.wells at comcast.net>