RE: Why the optimizer is not choosing the best plan?

See Wolfgang Breitling's work on the subject of Oracle pseudoerror debugging event 10053. Trace the optimizer's decision-making process. You'll probably discover either a mis-set instance parameter or that you've accidentally "lied" to the optimizer regarding data cardinalities, skew, or the like.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
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-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Sami Seerangan
Sent: Wednesday, October 20, 2004 2:49 PM To: Oracle Discussion List
Subject: Why the optimizer is not choosing the best plan?

Hi All,

I have 4 tables join query(all tables statistics are upto date) that is working fine if it goes for HASH_JOIN. But without HINT it is always doing NL_JOIN and takes about 50 secs to execute.

However using ORDERED hint it is going for HASH_JOIN and the response time got reduced to less than 5 secs, but we don't prefer to implement HINT based solution

Why the optimizer is not choosing the best execution plan(In this case hash_join rather than NL_join)?

-- 
Sami Seerangan
Oracle DBA
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