Re: ANALYZE Command

From: Just Visting <guest_at_example.com>
Date: Fri, 02 Jul 1999 22:49:35 GMT
Message-ID: <377d40e6.3341625@news>

In the past the cost based optimizer made some REAL BAD "choices". At which revision level of Oracle would you be 95% confident that the statement below is true & reliable?

For which versions (older than 7.x.y.z?) would the rule-based optimizer typically yield better results than the cost optimizer?

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On Fri, 02 Jul 1999 08:29:04 -0400, Kenneth C Stahl <BluesSax_at_Unforgettable.com> wrote:

>The whole purpose of ANALYST TABLE ..... COMPUTE STATISTICS; is to provide
>the programmer with information (although it is possible to glean
>interesting information from the statistics columns). The purpose is to make
>cost-based optimization work properly. Without the statistics all of your
>sql will be optimized by the rule-based optimizer and that means that you
>must be careful to tune the sql yourself and may necessitate multiple
>attempts as you run the statement through EXPLAIN to look at the execution
>path. Once you run statistics the cost-based optimizer will automatically
>rearrange your sql to use the most efficient execution path within the scope
>of the methods used by the cost-based optimizer. The cost-based optimizer
>may still get things done the most optimal way possible because it can
>select the wrong index or do other things that introduce inefficiencies into
>the execution, but for most cases it will do the optimization better than
>you can do it by hand.
>
>Ken
>
>Connor McDonald wrote:
>
>> flowerss_at_my-deja.com wrote:
>> >
>> > I've just started performance tuning a database
>> > and I don't understand the logic of the ANALYZE
>> > command. I ran the command; however, I don't
>> > understand how to make use of it. Specifically,
>> > the Endpoint_Number and Endpoint_Value Field?
>>
>
Received on Fri Jul 02 1999 - 17:49:35 CDT