Re: [Fwd: Re: [GENERAL] Unisersal B-Tree]

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Justin Clift <justin(at)postgresql(dot)org>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [Fwd: Re: [GENERAL] Unisersal B-Tree]
Date: 2001-05-04 19:56:10
Message-ID: 27662.989006170@sss.pgh.pa.us
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> ... Think of a query like this:
>
> select a,b,c from table where ( a>min_a and a<max_a ) and ( b>min_b and b<max_b )
>
> In a conventional implementation you have two indexes on attributes a and b.
> But to run this query the database engine profits only from one index. It has
> to run through all the values of the other. This gets even worse if you use more
> constraints, and this scheme is typical for things like OLAP.
>
> With the new methode you add one UB-index that embraces a and b. And you run
> only once through this index.

And this is different from a multicolumn btree index how?

I looked at the referenced website when this message first went by,
and was unhappy at the apparently proprietary nature of the technology
(not to mention the excessive hype ratio). I lost interest ...

regards, tom lane

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