All about product and Qlik solutions: scripting, data modeling, visual design, extensions, best practices, etc.
QlikView has a very efficient, patented caching algorithm that effectively eliminates the calculation time for calculations that have been made before. In other words, if you use the “back” button in the toolbar, or if you happen to make a selection that you have made before, you usually get the result immediately. No calculation is necessary.
But how does it work? What is used as lookup ID?
For each object or combination of data set and selection or data sub-set and expression QlikView calculates a digital fingerprint that identifies the context. This is used as lookup ID and stored in the cache together with the result of the calculation.
Here "calculation" means both the Logical Inference and Chart calculation - or in fact, any expression anywhere. This means that both intermediate and final results of a selection are stored.
There are some peculiarities you need to know about the cache…
The cache efficiently speeds up QlikView. Basically it is a way to trade memory against CPU-time: If you put more memory in your server, you will be able to re-use more calculations and thus use less CPU-time.
Further reading on the Qlik engine internals:
Symbol Tables and Bit-Stuffed Pointers
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