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From: Joachim Wieland on 8 Apr 2010 19:17
I'd like to revive the discussion about offering another compression
algorithm than zlib to at least pg_dump. There has been a previous
discussion here:

http://archives.postgresql.org/pgsql-performance/2009-08/msg00053.php

and it ended without any real result. The results so far were:

- There exist BSD-licensed compression algorithms
- Nobody knows a patent that is in our way
- Nobody can confirm that no patent is in our way

I do see a very real demand for replacing zlib which compresses quite
well but is slow as hell. For pg_dump what people want is cheap
compression, they usually prefer an algorithm that compresses less
optimal but that is really fast.

One question that I do not yet see answered is, do we risk violating a
patent even if we just link against a compression library, for example
liblzf, without shipping the actual code?

I have checked what other projects do, especially about liblzf which
would be my favorite choice (BSD license, available since quite some
time...) and there are other projects that actually ship the lzf code
(I haven't found a project that just links to it). The most prominent
projects are

- KOffice (implements a derived version in
koffice-2.1.2/libs/store/KoXmlReader.cpp)
- Virtual Box (ships it in vbox-ose-1.3.8/src/libs/liblzf-1.51)
- TuxOnIce (formerly known as suspend2 - linux kernel patch, ships it
in the patch)

We have pg_lzcompress.c which implements the compression routines for
the tuple toaster. Are we sure that we don't violate any patents with
this algorithm?


Joachim

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