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Re: [PATCH] COPY .. COMPRESSED

From: Claudio Freire <klaussfreire(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] COPY .. COMPRESSED
Date: 2013-01-16 02:44:45
Message-ID: CAGTBQpbTpWKHo4upnFL8BrM4VvHn+Rw3nuU44HEsNj4AERcPdg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Jan 15, 2013 at 7:46 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Compressing every small packet seems like it'd be overkill and might
>> surprise people by actually reducing performance in the case of lots of
>> small requests.
>
> Yeah, proper selection and integration of a compression method would be
> critical, which is one reason that I'm not suggesting a plugin for this.
> You couldn't expect any-random-compressor to work well.  I think zlib
> would be okay though when making use of its stream compression features.
> The key thing there is to force a stream buffer flush (too lazy to look
> up exactly what zlib calls it, but they have the concept) exactly when
> we're about to do a flush to the socket.  That way we get cross-packet
> compression but don't have a problem with the compressor failing to send
> the last partial message when we need it to.

Just a "stream flush bit" (or stream reset bit) on the packet header
would do. First packet on any stream would be marked, and that's it.


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