> > Thanks. Yes I know it's by no means trivial. I thought in case there was an > index on the column on which I want to place condition, the index machinery > itself can do the counting (i.e. when the index is updated, the counter is > incremented). It doesn't seem too orthogonal to the current implementation, > at least from my very limited experience. >
It's actually not that easy in Cassandra since a main feature is that the writes don't imply a read. But if you want your index to count the number of row where foo=bar, you need when a new column foo=bar is written to know if the column did not exist already in this row, in which cas you should not increment. Similarly, if you write foo=42, you need to check if the previous value was foo=bar and if yes decrement your index. -- Sylvain
