Gregory Stark wrote:
> "Heikki Linnakangas" <heikki@enterprisedb.com> writes:
>
>> That general approach of storing a common part leading part just once is
>> called prefix compression. Yeah, it helps a lot on long text fields.
>> Tree structures like file paths in particular.
>
> You kind of want to do avoid both the prefix and the suffix, no?
You're much more likely to find common prefixes than suffixes in an
index page, because of the ordering. I suppose compressing the suffix
would be useful in some cases as well. You might be better off with some
generic compression algorithm at that point, though.
>> It's been discussed before. One big problem is extracting the common
>> leading part. You could only do it for text,
>
> Or for multi-column indexes
Oh yeah, that you could do more easily.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com