Oracle-L: stats and query plans

From: Sai Selvaganesan <ssaisundar_at_sbcglobal.net>
Date: Sun, 10 Aug 2003 11:54:23 -0800
Message-ID: <F001.005C9EEA.20030810115423@fatcity.com>

a very basic question

i have faced this issue a few times in the last couple of weeks. we have a few queries that seem to run remarkable well in rule based optimisation than in choose based optimisation. the queries, with all the object stats collected upto date, never returns a result while when i deleted all stats it returns a result in no time.The plans are diffrent and w/o stats indexes are being used.

when this happens in the same system what are the things i should check. is it not recommended that oracle CBO is the best way to go in performance tuning and query optimisations.then how come rule based turns out to be efficient.surely i havent generated 10053 trace and gone through it but it doesnt make sense why CBO falters. Logically speaking when rule based path gives a result,CBO should choose that explain plan.

can someone throw some light on this

thanks
sai

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Author: Sai Selvaganesan
INET: ssaisundar_at_sbcglobal.net

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