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Hi,
I'd like to improve the performance of my QlikView application.
My idea is as follows:
there are 4 sheets in my application. The formuli (expressions) used on the 1st and the 2nd sheets are the same.
I see that QlikView recalculates the expressions if I switch from sheet1 to sheet2. It takes time.
Is it possible not to recalculate expressions if they have already been calculated?
Thank you in advance,
Larisa
Hi,
I am sorry I am responding in this old thread, but i was wondering about a statement you made:
" store identical formulas (expressions) in variables, and use the same variables everywhere, to ensure that the calculations are not repeated"
as far as I know those variables are just being used as text within the expressions. I believe I read it at several places that variables will not precalculate a expression but rather make it so that you do not need to type or copy paste the expression everywhere where you want to use it.
Could you give some more insight in this matter? as well perhaps rwunderlich ?
thanks in advance
The main advantage of using variables for formulas is the ease of maintenance. As far as performance is concerned, using variables helps ensuring consistency across your multiple expressions.
Identical expressions are cached in QlikView and the cache results are reused. However, even slight variances in spelling void the caching. For example, the following are three different expressions, from QlikView's standpoint:
SUM(Sales)
sum(Sales)
Sum (Sales)
So, these 3 expressions will get calculated 3 times, while the same expressions that use a variable, will get calculated once and reused 3 times.
That's the biggest impact on performance. In addition, if some of the calculations don't need to be "dimensional", these calculations can be optimized with variables that begin with an equal sign "=". They get calculated before the chart is calculated, so it might be beneficial to perform these calculations once and reuse them several times.
cheers,
Oleg Troyansky
Check out my new book QlikView Your Business - the Expert Guide to QlikView and Qlik Sense.
This is a nice piece of advice; thank you, Oleg!