Hello Philo Building bloom filter for column names (what you call column key) is technically possible but very expensive in term of memory usage.
The approximate formula to calculate space required by bloom filter can be found on slide 27 here: http://fr.slideshare.net/quipo/modern-algorithms-and-data-structures-1-bloom-filters-merkle-trees false positive chance = 0.6185 * m/n where m = number of bits for the filter and n = number of distinct keys For example, if you want to index 1 million of rows, each having 100 000 columns on average, it will end up indexing 100 billions of keys (row keys & column names) with bloom filter. By applying the above formula, m ≈ 4.8 * 10^11 bits ≈ 60Gb to allocate in RAM just for bloom filter on all row keys & column names ... Regards Duy Hai DOAN On Sun, Sep 14, 2014 at 11:22 AM, Philo Yang <ud1...@gmail.com> wrote: > Hi all, > > After reading some docs, I find that bloom filter is built on row keys, > not on column key. Can anyone tell me what is considered for not building > bloom filter on column key? Is it a good idea to offer a table property > option between row key and primary key for what boolm filter is built on? > > Thanks, > Philo Yang > >
