Re: CBO - Why does it often choose the Sort Merge Join?

On 25 Jan 2002 04:03:30 -0800, trundlebus1_at_hotmail.com (Ian) wrote:

>Hi,
>I've been doing some basic testing on sort/merge and hash joins and
>was wondering why the CBO often prefers to use the sort/merge join
>rather than the hash join?
>
>I can't find any documentation anywhere!
>
>Many thanks in advance
>
>Si

Can'tfind the documentation? That means that you haven't looked on Oracle's website!

Let me help you a bit.

Oracle8i Designing and Tuning for Performance Release 2 (8.1.6)
Part Number A76992-01
Chapter: 4, The Optimizer
Section: Optimizing Joins
Sub-Section: How the Optimizer Chooses the Join Method And
SubSection: Choosing Execution Plans for Join Statements Paragraph: Choosing Execution Plans for Joins with the CBO

You'll need to log in first.

The link to the first section is:
<URL:http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/a76992/optimops.htm#39473>

The link to the second paragraph:
<URL:http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/a76992/optimops.htm#36532>

That being said, you may want to read the entire chapter.

That being said you may want to read the entire book.

That being said you may want to read all the books.

That being said you may want to read....

HTH,
Brian Received on Fri Jan 25 2002 - 08:16:30 CST