Collect statistics

[sivatcs]

I am inserting into a table in teradata by selecting from 3 tables , it inserts some 7 lakh records and it is very slow.
If i have to use collect statistics before inserting into the table , can i use collect statistics for the columns or how do i go abt it.

Thanks in advance.

 

[dnoeth]

Hi sivatcs,
there's no need to collect stats before you insert, because the optimizer has no choice but only one way to do the insert.
But you should collect stats probably after the insert.

7 lakh = 700.000?
How large is your target table?
What's the Primary Index?
Is it partitioned?
Any Secondary Indexes/Permanent Journal/Join Indexes?
How fast is the select without insert?
How slow is "very slow"?

Dieter

 

[RogerCruse]

Hi,
Make sure you're not loading data in the Primary Index order as this won't use the full power of Teradata.

Also, I suggest you COLLECT STATS on each column / index before loading data into your table -

COLLECT STATS yourtable COLUMN col1;
COLLECT STATS yourtable COLUMN col2;
COLLECT STATS yourtable INDEX (col1, col2);
Etc.

Then after you've loaded your data, do a single non -specific COLLECT STATS to refresh these STATS-

COLLECT STATS yourtable;

While doing it this way won't improve the performance of your dataload, it will simplify and speed up the STATS collection a little.

Roger...