Re: [HACKERS] lztext.c

Tatsuo Ishii wrote:

> I'm going to commit changes to make lztextlen() aware of
> multi-byte. While doing the work, I found that no POSITION() or
> SUBSTRING() for lztext has been implemented in the file.

Thank's for that. I usually don't have multi-byte support
compiled in and it's surely better if you do the extension
and tests.

I know that a lot of functions are missing so far. Especially
comparision and the mentioned ones. I thought to get back on
it after the multi-byte support is inside.

> BTW, does anybody work on making lztext indexable? If no, I will take
> care of it with above addtions.

IMHO something questionable.

A compressed data type is preferred to store large amounts of
data. Indexing large fields OTOH is something to prevent by
database design. The new type at hand offers reasonable
compression rates only above some size of input.

OTOOH, it might get someone around the btree split problems
some of us encountered and which I where able to trigger with
field contents above 2K already. In such a case it can be a
last resort.

I'd like to know what others think.

Don't spend much efford for comparision and the SUBSTRING()
things right now. I already have an additional, generalized
decompressor in mind, that can be used in the comparision for
example to decompress two values on the fly and stop
comparision at the first difference, which usually happens
early in two random datums.

Tell me when you have the multi-byte (and maybe cyrillic?)
stuff committed and I'll take my hands back on the code.

Jan

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