Hi all, If I have the following table: CREATE TABLE t ( pk int, ck int, c1 int, c2 int, ... PRIMARY KEY (pk, ck) )
There are lots of non-clustering columns (1000+). From time to time I need to do a query like this: SELECT c1 FROM t WHERE pk = abc AND ck > xyz; How efficient is this query compared to SELECT * ...? Apparently SELECT c1 would save a lot of network bandwidth since only c1 needs to be transferred on the wire. But I am more interested in the impact on disk IO. If I understand C* storage engine correctly, one CQL row is clustered together on disk. That means c1 from different rows are stored apart. In the case of SELECT c1, does C* do multiple seeks to only lift c1 of each row from disk or lift the whole row into memory and return c1 from there? >From comments on https://issues.apache.org/jira/browse/CASSANDRA-5762 it seems C* lifts the whole row as of 1.2.7. Is this still the case on 2.1.*? Thanks.
