Re: AW: DDL Discussion continued

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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