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Home -> Community -> Mailing Lists -> Oracle-L -> RE: full-scan vs index for "small" tables
Yes, CBO can produce better plans. Specially were indexed access is impossible. Then one has to go into full scans and here CBO is pretty good. But OLTP is about "online".
OLTP SQL is programmed (well, has to be programmed) to be "online".
Here I can not think of much else than simple nested loops. Well, may be small lookup tables can be hash-joined, something like that.
If, however, OLTP relies on a full scan of fast growing table then this is a bad practices design, so frequent in those days.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Connor McDonald
Sent: 30. júní 2006 13:33
To: oracle-l_at_freelists.org
Subject: Re: full-scan vs index for "small" tables
Sheesh, people are really keen on bagging the CBO...Hell, we all know its trivial to produce scenarios where the CBO will get it wrong (inter-column dependencies always being a common one)..
But a little humility please...I've also had many times where I've seen a plan and thought..."Nah, CBO has got it wrong"...so I hint it in the way that I think will be best, and guess what, my option sucks and the CBO's choice was better...Man, we all stay quiet on that one don't we...
:-)
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Connor McDonald
"Semper in excremento, sole profundum qui variat"
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Received on Fri Jun 30 2006 - 09:02:30 CDT
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