Re: [HACKERS] LZ compressing data type

>
> >
> > 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).

It't an SLZ algorithm, not LZW. There are FLZ and LZ77 out
too (and I don't know how many other subtypes). At least, LZ
is a family of compression algorithms where LZW is just a
member of them.

I've written the entire code from scatch, inspired by an
article from Adisak Pochanayon dated back in 1993. If they
have a license on this algorithm, they have one on code that
can be coded from scatch in 20 hours after reading
information that's claimed to be free on the internet,
congrats.

This is M$ practice, I never thought that there's more than
one company out doing this kind of business.

But thanks for the info.

Jan

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