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Indexes in Teradata

Indexes

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Primary Index

Mandatory index

Only one PI for table

We can take a P.I till 64 columns[API is composite till 64 column]

If is physical mechanism to assign a row to amp

It effects a data distribution

OPI takes only unique values

NUPI takes duplicate and null values

PPI for range base query

If don’t specify any query system creates PI by default

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Real Time Advantages

For better distribution (or) uniform distribution

For better access plan

For better retrieval

For better join plan

As it is single Amp operation performs it is operation faster etc.

 

Creating Alternating Droping

We cannot drop P.I[it we want to drop PI. The table first and then change the PI]

The table is empty we can alter PI

The table is having data we cannot alter PI

 

PI Usage

Generally we take in the below situation

Frequently used column

Frequently used no- indexed column in the where clause 

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No primary index in where clause

i) If you are not able to decide and which columns

ii) We go for PI than create No PI, So that no distribution happens

iii) Whenever we fell comfortable then we convert NOPI

IV) Available NOPI from tera data 13 onwards.

 

No PI real time usage

a) Loading data into stage tables

b)Using FL and T pump Array insert at the time FL and T pump array insert etc.

 

Hash Map

It is created at the time of tera data soft installation It’s provides the relationship b/w Amp’s address [basic number] And row host values it the no. of the an same in the two system hash map it also be same

For Indepth knowledge on Teradata click on:

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Indexes in Teradata
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