It only reads till that column (a sequential scan, I believe) and do not read the whole row. It uses a row-level column index to reduce the amount of data read.
Much more details at (first 2-3 are must-reads in fact): http://thelastpickle.com/blog/2011/07/04/Cassandra-Query-Plans.html http://www.datastax.com/documentation/cassandra/1.2/webhelp/index.html?pagename=docs&version=1.2&file=#cassandra/dml/dml_about_reads_c.html http://www.roman10.net/how-apache-cassandra-read-works/ http://wiki.apache.org/cassandra/ArchitectureInternals Regards, Shahab On Fri, Sep 6, 2013 at 6:28 AM, Sridhar Chellappa <schellap2...@gmail.com>wrote: > Folks, > > When I read Column(s) from a table, does Cassandra read only that column? > Or, does it read the entire row into memory and then filters out the > contents to send only the requested column(s) ? >
