Re: [HACKERS] LZ compressing data type - Mailing list pgsql-hackers

From Michael Simms
Subject Re: [HACKERS] LZ compressing data type
Date
Msg-id 199911172354.XAA00481@argh.demon.co.uk
Whole thread Raw
In response to LZ compressing data type  (wieck@debis.com (Jan Wieck))
Responses Re: [HACKERS] LZ compressing data type  (wieck@debis.com (Jan Wieck))
List pgsql-hackers
> 
> Hi,
> 
>     I just committed some changes that require an initdb.
> 
>     New  are  the  discussed,  simple  LZ compressor, placed into
>     /utils/adt/pg_compress.c, and a new lztext data type based on
>     it.   You'll  find  a  fairly  detailed  description  of  the
>     compression  algorithm  in  the  comments  at  the   top   of
>     pg_lzcompress.c.

One question.

You say this is an LZ algorythm. Is this the same as LZW, as in the
same kind that gifs use. If so, are we sure that this algorythm is not
covered by the Unisys patent? Their patent is on the algorythm for
compression not on gifs themselves. 

If it is, you are liable for a $5,000 fee to use it throughout your
site, or a per-licence fee if you are distributing (thay are worked out
on a per case basis but typical licences are $5 per unit sold from what
I am told).

I came across this problem with a gif manipulation program that *I
WROTE FROM SCRATCH* and had to switch to using the libungif
compression routines.

Just thought Id mention this, in case it has been overlooked.
                    ~Michael


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