Partitioning

General
Enthusiast

Partitioning

I understand the PARTITION#Ln is used to denote a level in MLPPI.

What is the combined partitioning Expression ? Is this all the ranges specified in a MLPPI table. ?

How does the RowKey differ to the combined partition number. 

Teradata's documentation states the following.

The combined partitioning expression for a table defines how rows are ultimately partitioned on each AMP. The result of the combined partitioning expression for specific values of the partitioning column is referred to as the combined partition number.

Thanks

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4 REPLIES
Senior Apprentice

Re: Partitioning

The combined partitioning expression is the PARTITION number, which is calculated on based on the number of PARTITION#Ln in each Level, basically a number between 1 and the product of the number of partitions in each level:

http://www.info.teradata.com/HTMLPubs/DB_TTU_15_00/SQL_Reference/B035_1184_015K/Create_Table-Details...

The RowKey is based on PARTITION, so there's no difference between single and multi-level PPI.

Enthusiast

Re: Partitioning

Thanks Dieter your explanation has cleared it up for me. Knowing the combined partitioning expression is the partition Number makes everythng else I read now clear. Many Thanks

New Member

Re: Partitioning

Hi   We are a Teradata 14.10 site. Is there any way to directly parition on a Varchar column in Teradata ?   I want to partition on a multi billion table on a Varcr(18) column. Currrently there are approximately 8500 distinct values for this colun, so I can't specify a case statement large enough.   If I specify the colums as patrtition on VARCHAR_COLUMN_NAME,  Teradata cast the coulumn as Integer.

Senior Apprentice

Re: Partitioning

How is this column accessed?

Using equality on a single value: WHERE VarCharCol = 'value'?