Each part within the set analysis or anywhere else in an expression must be evaluated and will in general have an impact on the calculation. If there is a better approach then your used one is difficult to say because the needed calc-times are essentially depending from your datamodel and if you used any kind of simplifying to the expressions through an external storing you will need to find your balance between performance, simplicity and maintainability.
I don't use such external storing of expressions unless a few ones which come from include-variables because in my environment it would cause more work and disadvantages as benefits.
Nevertheless I try to avoid redundancy and to simplify the logic and this is quite often be done with variables, variables with parameter or with flags. Here a few examples:
set var = ", PeriodFlag = {'YTD'}";
or maybe another one
set var = " ";
sum({< Field = {'value'} $(var) >} value)
For such an approach you will probably need some kind of if-loop to return the appropriate value.
Quite more often used are variables with parameter like:
set var = "sum({< PeriodFlag = {'$1'}>} value)";
which is then called with:
$(var(YTD))
or the flag is just use as multiplicator like:
sum(value * YTD) or sum(value) * YTD
Essential for the above suggestion is that at least one master-calendar is applied with one or multiple flags and/or an additionally As-Of-Table is created for the flag(s).
It may not look like an answer to your question but I think it may be useful to simplify your expression-handling.
- Marcus
