Re: [PATCH 08/16] Introduce the ApplyCache module which can reassemble transactions from a stream of interspersed changes - Mailing list pgsql-hackers

From Andres Freund
Subject Re: [PATCH 08/16] Introduce the ApplyCache module which can reassemble transactions from a stream of interspersed changes
Date
Msg-id 201206281804.26084.andres@2ndquadrant.com
Whole thread Raw
In response to Re: [PATCH 08/16] Introduce the ApplyCache module which can reassemble transactions from a stream of interspersed changes  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: [PATCH 08/16] Introduce the ApplyCache module which can reassemble transactions from a stream of interspersed changes
List pgsql-hackers
On Thursday, June 28, 2012 06:01:10 PM Robert Haas wrote:
> On Tue, Jun 26, 2012 at 8:13 PM, Andres Freund <andres@2ndquadrant.com> 
wrote:
> > It even can be significantly higher than max_connections because
> > subtransactions are only recognizable as part of their parent transaction
> > uppon commit.
> 
> I've been wondering whether sub-XID assignment was going to end up on
> the list of things that need to be WAL-logged to enable logical
> replication.  It would be nicer to avoid that if we can, but I have a
> feeling that we may not be able to.
I don't think it needs to. We only need that information during commit and we 
have it there. If a subtxn aborts a separate abort is logged, so thats no 
problem. The 'merging' of the transactions would be slightly easier if we had 
the knowledge from the get go but that would add complications again in the 
case of rollbacks.

What do you think we need it?

Greetings,

Andres
-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services


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