PL/SQL forall operator speeds 30x faster for table inserts

Question

Hi!
I find this quotes from one internet website. According to this site - "Loading an Oracle table from a PL/SQL array involves expensive context switches, and the PL/SQL FORALL operator speed is amazing. " But, i knew something opposite - that normal SQL insertion always faster than this one. There may be some exception - but not always. Pls go through the link --
[url http://www.dba-oracle.com/oracle_news/news_plsql_forall_performance_insert.htm]PL/SQL FORALL operator speed is amazing In Oracle .
Anyone who have knowledge regarding this - pls share their views or opinion here to clear my doubt. I'll be waiting for the reply. Thanks in advance.
Regards.
Satyaki De.

Answer 1

Hi Satyaki,
The forall bulk processing is always faster than the row by row processing as shown in this test.
It is faster because you have much less executions of the insert statement and therefore less context switches.
I must mention that bulk fetching 100,000 records at a time isn't always a great idea for production code because
you'll use a large amount of PGA memory.
I guess you are confused with the "insert into products select * from products" variant. This pure SQL will beat the
forall variant.
From slow to fast:
1. row by row dynamic SQL without using bind variables (execute immediate insert ...)
2. row by row dynamic SQL with the use of bind variables (execute immediate insert ... using ...)
3. row by row static SQL (for r in c loop insert ... values ... end loop;)
4. bulk processing (forall ... insert ...)
5. single SQL (insert ... select)
Hope this helps.
Regards,
Rob.
Message was edited by:
Rob van Wijk
Way too late ...