Re: Re: xReader, double-effort (was: Temporary tables under hot standby)

On Fri, Apr 27, 2012 at 11:18 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> wrote:

> I'm not convinced that I would rather see the logic fixed inside the
> master as opposed to being deployable on the master's machine, the
> slave machine, or even on its own machine in between.

There are use cases where the translation from WAL to logical takes
place on the master, the standby or other locations.

It's becoming clear that filtering records on the source is important
in high bandwidth systems, so the initial work focuses on putting that
on the "master", i.e. the source. Which was not my first thought
either. If you use cascading, this would still allow you to have
master -> standby -> logical.

Translating WAL is a very hard task. Some time ago, I did also think
an external tool would help (my initial design was called xfilter),
but I no longer think that is likely to work very well apart from very
simple cases.

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 Simon Riggs                   http://www.2ndQuadrant.com/
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