Re: prefix btree implementation

Qingqing Zhou wrote:
> I am not sure if this idea was mentioned before.
> 
> The basic prefix btree idea is quite straightforward, i.e., try to
> compress the key items within a data page by sharing the common prefix.
> Thus the fanout of the page is increased and the benefits is obvious
> theorectically.
> 
<snip>
> 
> So together, there are basically four types of possible sharing:
> column-wise (case 1), character-wise (case 2), column-character-wise (case
> 3), and byte-wise (case 4).
> 
Oracle implements something similar called index compression, but I believe it
is only for common column values. I haven't checked in versions>9r1 so maybe
there are other options implemented by now.

Jonathan Lewis describes some pros and cons here:
http://www.jlcomp.demon.co.uk/faq/compress_ind.html

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