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Re: Anyone have a well normalized DB2 database and use RPG?



fixed

That is the idea. The rules are the same, the performace has changed, then you don't need to de-normalize anymore, in this particular situation, wich is rery frecuent.

CRPence wrote:

On 10/29/13 3:25 PM, Raul A. Jager W. wrote:

It is usual to put a "balance" in master files, even if in a
normalized database must be calculated as the sun of the
transactions. This because cost of sum, but in 7.1 you can create an
EVI over the transaction table, and get the sum very fast, so no need
to "de-normalize" to gain performance.


Specifically, *if* the Encoded Vector Index is created with the appropriate "EVI INCLUDE aggregates" that match the aggregates that will be requested in such a query.

http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/topic/rzajq/idxgrpingimp.htm
_i Index grouping implementation i_
"There are two primary ways to implement grouping using an index: Ordered grouping and pre-summarized processing.
...

_EVI INCLUDE aggregates_

A more powerful example of pre-summarized processing can be facilitated by the use of the INCLUDE keyword on the index create. By default, COUNT(*) is implied on the creation of an EVI. Additional numeric aggregates specified over non-key data can further facilitate pre-determined or ready-made aggregate results during query optimization.

For example, suppose the following query is a frequently requested result set, queried in whole or as part of a subquery comparison.

SELECT AVG(col2)
FROM t1
GROUP BY col1

Create the following EVI to predetermine the value of AVG(col2).

CREATE ENCODED VECTOR INDEX eviT1 ON t1(col1) INCLUDE(AVG(col2))
..."







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