Re: Cancelling idle in transaction state

Added to TODO:
	
	Allow administrators to cancel multi-statement idle
	transactions
	
	    This allows locks to be released, but it is complex to report the
	    cancellation back to the client.
	
	        * http://archives.postgresql.org/pgsql-hackers/2008-12/msg01340.php 

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Simon Riggs wrote:
> Currently SIGINT is ignored during <IDLE> in transaction, but we have
> recently agreed to allow this to cancel the transaction. We said we
> would do this in all cases, so this is a separate feature/patch (though
> Hot Standby requires it).
> 
> A simple change allows the transaction to be cancelled, but there are
> some loose ends that I wish to discuss.
> 
> If we are running a statement and a cancel is received, then we return
> the ERROR to the client, who is expecting it. If we cancel a transaction
> while the connection is idle, we have no way of signalling to the client
> program this has occurred. So the client finds out about this much
> later, not in fact until the next message is sent.
> 
> Is there a mechanism for communicating the state back to the client?
> Will this be handled correctly with existing code? psql appears to be
> confused by a cancelled backend.
> 
> I'm not familiar with these aspects of the code, so some clear
> suggestions are needed to allow me to work this out. I'm worried that
> this will delay things further otherwise.
> 
> -- 
>  Simon Riggs           www.2ndQuadrant.com
>  PostgreSQL Training, Services and Support
> 
> 
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-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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