Insert performance in empty PPI table V16.20

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Insert performance in empty PPI table V16.20

Hey I'm trying to insert ~300M record into a table for which the partitions are empty. But it is taking very long, while I tried in an empty table it gets

successfully within 2 minutes. PFB SQL query.

 

Why there is a difference in performance, can you please explain.

 

CASE 1

DELETE table A

where partition=X



insert into A

select * from B where partition=B;

--300M inserted with 5 mins



CASE 2:



Create table C as A with no data;



insert into C

select * from B where partition=B;

-- 300 M inserted in 2 mins.