Re: AW: DDL Discussion continued

[vhamberg@xxxxxxxxxxx]

Charles

Spot on! Not sure where Dave is getting his information for this one, but logical files have been radix indexes probably since the 38 days.

Here is something from a data warehouseing redbook from 1998 - NOTE THE YEAR - 1998! Heh!

3.2.3.1 Binary Radix Tree Index
The Binary Radix Tree Index (B-tree index) has served DB2/400 for years. B-tree
index is a multi-level structure. There is always a root node with entries pointing
to the other level of the tree?s nodes. At the lowest level, the so-called leaves
contain the relative addresses of the records. The bit representation of the key
value is used. In the example in Table 6 on page 29, instead of bit representation,
we work with the arrays of characters as values of the key field. Nevertheless, the
example shows how the B-tree indexes are built and how you navigate through
them to find a specific record in the table. Imagine that there is a table where a
field containing the name of the supplier is a key.

There is an example that shows how it works. It is an extremely efficient retrieval structure - I seem to recall that most probes into an index go down no more than 3 or 4 levels, seems I heard that in the early 90s

Regards
Vern

 -------------- Original message ----------------------
From: "Charles Wilt" <charles.wilt@xxxxxxxxx>
> On Thu, Sep 25, 2008 at 8:01 PM, Dave Odom <Dave.Odom@xxxxxxxxxxxx> wrote:
> > Indexes are a different animal than regular LFs.   A radix index, for example, 
> is WAAAAY different than a old style LF or even an SQL View, even though it says 
> it's a LF.
>
> I don't think so.
>
> An SQL index and a keyed DDS logical are both radix indexes.  Thus the
> reason you can share the "access path" (aka index) created via SQL
> with a DDS defined logical.
>
> Now an SQL EVI index is indeed a way different animal than a radix index.
>
>
> Charles Wilt
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