topic Re: Query about QlikView in QlikView

Query about QlikView

Fri, 09 Nov 2012 21:27:16 GMT

i have read in what makes Qlikview unique white paper the following sentence :

QlikView achieves a significant reduction in the size of the data used for analysis using a data dictionary (a hash table) and by using only the number of bits required

what QlickView mean by this sentence ?

Regards

Re: Query about QlikView

whiteline — Sat, 10 Nov 2012 08:44:58 GMT

Hi.

This means, if you have duplicates values in a field. It's stored only once. For all other occurances QV just stores the index number wich usually has less size than a original string value.

Re: Query about QlikView

hic — Sat, 10 Nov 2012 19:40:20 GMT

... and in addition, the "index number" is a bit-stuffed pointer. I.e. a pointer that just uses the number if bits (not bytes) it takes to represent all distinct values of the field. For example, if a field has exactly 4 distinct values, QlikView uses a pointer with just 2 bits to represent all values of that field. The result is that all data tables (using these pointers) are minimal in size.

When the clear text is needed, this is fetched from the symbol table: the table with the distinct values, that is a mapping between the bit-stuffed pointers and the real value.

HIC