Re: Optimizer : query rewrite and execution plan ?

On Feb 6, 2008, at 7:35 AM, Roberts, Jon wrote:

>
>>> Since the SQL is not your fault and difficult to control, it is an
>>> argument in favour of an optional planner mode that would perform
>>> additional checks for redundant clauses of various kinds. The
> default
>>> for that would be "off" since most people don't suffer from this
>>> problem. BO isn't the only SQL generating-client out there, so I
> think
>>> this is a fairly wide problem.
>>
>> I would have to disagree. I spend a lot of time writing code that
>> generates SQL from a business app and feel strongly that any
>> optimisation is my responsibility.
>>
>
> The point to a BI tool like BO is to abstract the data collection  
> and do
> it dynamically.  The SQL is built at run time because the tool is
> designed to give the end user as much flexibility as the data  
> structure
> allows to query the data however they want.
>
> It isn't feasible, possible, or recommended to rewrite all of the
> possible generated SQL that could be designed at runtime by the tool.

No, but it is feasible to expect the tool to generate well-formed  
queries without redundant clauses.  There are plenty that do.

Erik Jones

DBA | Emma®
erik@myemma.com
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615.292.0777 (fax)

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