Re: How are joins performed when using a database link?

From: Frank <fvanbortel_at_netscape.net>
Date: Tue, 18 Mar 2003 20:46:01 +0100
Message-ID: <3E777779.9080706@netscape.net>

DA Morgan wrote:
> Rob Cowell wrote:
>
>

>>DA Morgan wrote:
>>
>>>Rob Cowell wrote:
>>>
>>>
>>>><snipped>
>>>>
>>>>
>>>>>it often happens here that guys spend more time typing out a request
>>>>>for advice than actually having a go, making a few mistakes & testing
>>>>>things out.
>>>>
>>>>I think you are being a bit harsh on this poster.
>>>
>>>You are correct with respect to how it works. But incorrect with respect to the
>>>basic premise which is the impact on performance.
>>>
>>>In less time than it took to post the request and wait for a response the OP
>>>could have run a test. And while not knowing "how it worked" would sure know
>>>the relative performance on THEIR system.
>>>
>>>Daniel Morgan
>>
>>So he would have known what improved performance on this particular
>>query on this system but not why, or how to find out why.
>>He would have been back to square one with the next problem of this
>>type, and in no position to think about how to solve a more complex
>>distributed problem.
>>
>>I appreciate there are a lot of people who don't seem to be able to find
>>a freely available manual but I don't think this topic is particularly
>>well explained anywhere obvious.
>>
>>Let's face it most problems here can be solved if you want to plow
>>through Metalink and make some empirical discoveries.

>
>
> Lets try it your way. Lets assume an engineer from Oracle, one that wrote the
> underlying C code sent him a copy of the source code along with full documentation on
> how it works.
>
> Of what possible value would that be? The only things that matter are performance,
> scalability, and stability. I don't know the underlying engineering differences
> between an Intel P2 CPU and an Intel P4 CPU. But I can sure tell you which one I want
> to use to support an application.
>
> Lets let this one drop but while I agree that it is nice to know ... how ... it has
> limited utility.
>
> Daniel Morgan
>

It used to be in one of the internal Oracle Basic SQL Tuning books... "Consider remote views if large joins are performed over database links."

I think this type of knowledge is the basis for good design/coding.

-- 
Regards, Frank van Bortel

Received on Tue Mar 18 2003 - 13:46:01 CST