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From "Laura Stewart" <scotsmat...@gmail.com>
Subject Re: Tuning question - from 10.2 Doc Reviews
Date Fri, 06 Oct 2006 16:56:16 GMT
On 10/2/06, Laura Stewart <scotsmatrix@gmail.com> wrote:
> Hi -
>
> In the 10.2 Doc Review of the Tuning Guide
> http://wiki.apache.org/db-derby/TuningTenTwo
> there is this comment:
>
> In the file
> http://db.apache.org/derby/docs/dev/tuning/rtuntransform472.html
> there is a mention of rewriting queries:
>
>  "Users can work around this possibility by writing the query like
> this (which is not optimizable):(country... ) LIKE ?".
>
> But this does not mention the rationale for doing so, which could be
> benefical for the users in understanding the transformation.
>
> One thought is that specifying "(country || '')" disables the
> transformation because "(country || '')" evaluates to a Concatenate
> node instead of a ColumnReference, which makes the expression "not
> optimizable" and thus the transformation is skipped.
>
> Does anyone have any additional information as to why "(country ||
> '')" should be specified?

Unless someone posts additional information by Monday, I will update
the documentation with the explanation above for using "(country || >
"')"

-- 
Laura Stewart

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