On 2014-12-12 09:24:27 -0500, Bruce Momjian wrote:
> On Fri, Dec 12, 2014 at 03:22:24PM +0100, Andres Freund wrote:
> > > Well, the larger question is why wouldn't we just have the user compress
> > > the entire WAL file before archiving --- why have each backend do it? 
> > > Is it the write volume we are saving?  I though this WAL compression
> > > gave better performance in some cases.
> > 
> > Err. Streaming?
> Well, you can already set up SSL for compression while streaming.  In
> fact, I assume many are already using SSL for streaming as the majority
> of SSL overhead is from connection start.

That's not really true. The overhead of SSL during streaming is
*significant*. Both the kind of compression it does (which is far more
expensive than pglz or lz4) and the encyrption itself. In many cases
it's prohibitively expensive - there's even a fair number on-list
reports about this.


Andres Freund

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

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