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johnsunnydew 43 posts Joined 09/14
26 Jan 2015
Skew Factor & Stats

Hi,
I am quite new here to Teradata...Can anyone help me onthe query.. I am looking out for skew factors for certain tables.I would like to know the query for the same and what would be the desired value or range which is acceptable.
 
Also i would like to know the query to see for what all columns of a table the stats is already collected and what is not collected. Appreciate your help ASAP.
 
tHANKS 
sUNNY

Raja_KT 1246 posts Joined 07/09
26 Jan 2015

Hi,
You can have a look at this link(look till the end):
 http://www.info.teradata.com/HTMLPubs/DB_TTU_14_00/index.html#page/Database_Management/B035_1094_111A/ch09.050.139.html
One way is you  can have a look at dbc.statsv and verify too in  the qrylog table or dbql

Raja K Thaw
My wiki: http://en.wikipedia.org/wiki/User:Kt_raj1
Street Children suffer not by their fault. We can help them if we want.

johnsunnydew 43 posts Joined 09/14
27 Jan 2015

tHANKS.
One quick question..do we need to refresh a view once we collect stats for its underlying table?

Raja_KT 1246 posts Joined 07/09
27 Jan 2015

You dont need to refresh. I think you come from Oracle background, where you see materialized view, where  you can refresh.

Raja K Thaw
My wiki: http://en.wikipedia.org/wiki/User:Kt_raj1
Street Children suffer not by their fault. We can help them if we want.

johnsunnydew 43 posts Joined 09/14
27 Jan 2015

Hia thanks Raja..One more question..I am querying on a database to find the skeness of all tables..The result shows me including that of the stored procedures too and all stored procedures shows skeness of greate than 90..Is there something wrong?

ToddAWalter 316 posts Joined 10/11
27 Jan 2015

Skew should not be considered important for any object smaller than a few data blocks per AMP. There is just not enough statistical distribution to get an even distribution. And skew for very small objects will not cause a noticeable performance issue. SPs are very small and each is purposely stored on a single AMP so they will always be skewed.

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