Re: Insert performance (OT?)

nobody ?

On 18 Jul 2005, at 21:29, Yves Vindevogel wrote:

> Hi,
>
> Suppose I have a table with 4 fields (f1, f2, f3, f4)
> I define 2 unique indexes u1 (f1, f2, f3) and u2 (f1, f2, f4)
>
> I have 3 records
> A, B, C, D (this will be inserted)
> A, B, C, E (this will pass u2, but not u1, thus  not inserted)
> A, B, F, D (this will pass u1, but not u2, thus not inserted)
>
> Now, for performance ...
>
> I have tables like this with 500.000 records where there's a new 
> upload of approx. 20.000 records.
> It is only now that we say index u2 to be necessary.  So, until now, I 
> did something like insert into ... select f1, f2, f2, max(f4) group by 
> f1, f2, f3
> That is ok ... and also logically ok because of the data definition
>
> I cannot do this with 2 group by's.  I tried this on paper and I'm not 
> succeeding.
>
> So, I must use a function that will check against u1 and u2, and then 
> insert if it is ok.
> I know that such a function is way slower that my insert query.
>
> So, my question ...
> How can I keep the same performance, but also with the new index in 
> mind ???
>
>
> Met vriendelijke groeten,
> Bien à vous,
> Kind regards,
>
> Yves Vindevogel
> Implements
>
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Met vriendelijke groeten,
Bien à vous,
Kind regards,

Yves Vindevogel
Implements