The QlikView calculation engine
QlikView is very clever in how it does its calculations. As well as the data storage, as discussed earlier in this chapter, it also stores the binary state of every field and of every data table dependent on user selection—essentially, depending on the green/white/grey state of each field, it is either included or excluded. This area of storage is called the state space and is updated by the QlikView logical inference engine every time a selection is made. There is one bit in the state space for every value in the symbol table or row in the data table—as such, the state space is much smaller than the data itself and hence much faster to query.
There are three steps to a chart being calculated:
- The user makes a selection, ...