Re: Ingress Knowledge Management - Statistics-Based Optimizer

From: Sandor Nieuwenhuis <>
Date: 10 Aug 92 12:19:49 GMT
Message-ID: <>

In article <> (Tony Jambu) writes:
>In article <gavin.713173622_at_mulgulgum>, gavin_at_asis.unimelb.EDU.AU (Gavin Trigg)
>> (Richard Rabin) writes:

 stuff deleted
>> The statistics based optimizer is part of the base package. I understand that
>> Sybase operates in a similar way. I seem to remember reading somewhere lately
>> that Oracle was working on something similar, anyone know?
>Yes, Oracle now has a statistical optimiser. It can be found in the
>Version 7 of Oracle. I have not had much experience with it but can tell
>you that is is what I call a 'half-baked' statistical optimiser.
 [ ...stuff deleted ]
>Oracle on the other hand, only stops the query when the limit has been
>reached ie. after the event has occurred.

Allthough there is some common data, I would not say that the Resource limiter is the same as the query optimiser, so saying that thet statistical optimiser in ORACLE7 is 'half-baked', just because there is something you don't like in the Resource limiter, misses the point don't you think ?

The statistical optimiser in ORACLE7 has a lot of nice features, but I won't go in to that, otherwise people might think this is marketing hype.

On the subject of the Resource limiter, there are a lot of situations where checking before the query starts is not what you want. It will be completely dependent of the correctness of the statistics, if they are wrong, some queries might be stopped in advance, allthough they could have be run without problems.

A number of other limits are impossible to check in advance, like maximum resource limits per session (instead of per statement) or total connect time etc.

Sandor Nieuwenhuijs
Oracle Netherlands

I speak for myself and not for Oracle Corporation

  • No flames please ------
Received on Mon Aug 10 1992 - 14:19:49 CEST

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