Re: hash joins and pga/temp space?
- From: "Gints Plivna" <gints.plivna@xxxxxxxxx>
- To: alberto.dellera@xxxxxxxxx
- Date: Wed, 15 Nov 2006 10:03:58 +0200
And if you accidentally don't have Lewis' book then you can get some
insight of hash joins in one article and one presentation:
http://www.cs.ust.hk/vldb2002/VLDB2002-proceedings/papers/S29P03.pdf
http://www.pythian.com/documents/Working_with_Automatic_PGA.ppt
Although none of them directly answers to your question...
Gints Plivna
2006/11/15, Alberto Dell'Era <alberto.dellera@xxxxxxxxx>:
The algorithm Oracle uses for hash joins is wonderfully explained starting
on page 319 of Jonathan Lewis' "Cost Based Oracle", including the memory
management and even some events that may help you answer most
of your questions about memory sizing. With figures too :)
There are three variants of the hash join - optimal, one-pass and
multipass - the last one relies heavily on temp for storing intermediate
results, the first one uses only memory.
I'd suggest that you take a look to the book - it's a difficult topic
and I can't claim to have mastered it completely ;)
regards
Alberto
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