Le jeudi 31 janvier 2013 à 09:49 +0100, Pavel Stehule a écrit :
> any join where result is related to some function result can be very
> slow, because estimation will be out and any repeated function
> evaluation is just expensive.
>
Hi Pavel,
Thank you for the correction. Since we're at it, I have a question
regarding functions in a query :
Suppose I have a query of the form
SELECT my_function(column_1), column_2
FROM my_table
GROUP BY my_function(column_1)
ORDER BY my_function(column_1);
where my_function is a user defined function.
How many times is the function computed?
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Salutations, Vincent Veyron
http://marica.fr/site/demonstration
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