On Tue, Mar 25, 2008 at 01:46:51PM +0100, Zeugswetter Andreas OSB SD wrote:
> > So, I finally decide to focus on the project idea of improving hash
> > index now. It's more valuable , and also challenging.
> >
> > Any suggestion about the project idea of improving hash index?
>
> Imho one thing to look into is the storage. I do not see any real value
> in storing the key itself (especially longer keys) in the hash buckets.
> Instead store the hash value only (or not even that) and mark the index
> lossy (recheck the key in the heap).
>
> Andreas
>
Meng,
I had started a thread on the hackers mailing list about improving
the hash index in PostgreSQL. You can look through it for some of
the ideas that were suggested. The first one is to replace the storage
of the key values in the index with the hash of the key values instead.
This can leverage the lossy index heap re-check code that is already in
the database. Neil Conway had posted a patch doing this with an old
version of PostgreSQL. My coding skills are a bit rusty and my job has
kept me from making much progress towards this. Anyway, please take
a look at the hash index thread in hackers. It starts with:
http://archives.postgresql.org/pgsql-hackers/2007-09/msg00051.php
Let me know what you think?
Cheers,
Ken Marshall