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Karl Reitschuster

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Updated: 17 hours 43 min ago

Conditional Unique Indexes

Fri, 2013-05-17 03:25

Matrix : What you must learn is that these rules are no different than rules of a computer system. Some of them can be bent, others can be broken. Understand?
 
Usually an unique index grants the uniqueness of all rows in a specific table which have non-null values; But what if some data depended on a given business type in the the row of table needs to be unique and some not? combining function based index feature from Oracle with a unique index makes this possible.

--
-- SCOPE : OASIS
--
-- DDL:CALLITEMS_UK01           :INDEX.MOD              - TEST
--

DROP   INDEX CALLITEMS_UK01;
CREATE UNIQUE INDEX CALLITEMS_UK01
       ON    CALLITEMS
             ( CASE UNIQUE_REF WHEN 1 THEN UPPER(TRIM(ITEMCODE)) ELSE NULL END
             , CASE UNIQUE_REF WHEN 1 THEN ITEMTYPE ELSE NULL END
             , CASE UNIQUE_REF WHEN 1 THEN ACTIVESINCE ELSE NULL END  )
  TABLESPACE OASISIXM
;

 

Dependend on the uniqeness flag UNIQUE_REF a row may be unique to others or not. Maybe this makes sense for specific call item types. In our project a CALLITEMTYPES table controlled the unqueness of specifc call item types , pupulating the UNIQUE_REF flag to the CATLLITEMS table.

cheers

/K

 

 


InfoQ : Running the Largest Hadoop DFS Cluster

Wed, 2013-03-20 07:46

Since I joined a Big Data Event : Frankfurter Datenbanktage 2013 - I started to take also a look to non-relational technics too. The RDBMS is not for every asepct the correct and fitting and fulfilling answer to all data related IT challenges. 

Frequently I wondered about how facebook could handle such an dramatic amount of users and data growth. I found an interesting presentation from the facebooks HDFS - Development-Lead Hairong Kuang optimizing HDFS (Hadoop DFS) for Scalability, Storage Effiency and Availability.

An RDBMS would not scale to that amount of load - reasons for that is the explained in theory with the CAP-Theorem which I will post about later;

Now to the presentation on InfoQ :  http://www.infoq.com/presentations/Hadoop-HDFS-Facebook

enjoy

/

Karl