I understand that all insert operations will come to commitlog first, and Memtable second, after that it will be compacted to SSTable.
After compaction to SSTable, I perform an update operation for an existing column.
Must the SSTable be changed to update the value of that column?
http://wiki.apache.org/cassandra/MemtableSSTable says:
Your updated value will be written to commitlog, and a memtable, and will eventually be flushed to a new SSTable on-disk. Later, this SSTable may be merged with other SSTables to form a new larger SSTable (and the old ones will be discarded) – this is the compaction stage.