Your update doesn't go directly to an sstable (which are immutable), it is first merged to an in-memory table. Eventually the memtable is flushed to a new sstable.
See http://wiki.apache.org/cassandra/MemtableSSTable On Sat, Aug 11, 2012 at 11:03 AM, Aaron Turner <synfina...@gmail.com> wrote: > So how does that work? An sstable is for a single CF, but it can and > likely will have multiple rows. There is no read to write and as I > understand it, writes are append operations. > > So if you have an sstable with say 26 different rows (A-Z) already in > it with a bunch of columns and you add a new column to row J, how does > Cassandra store the column/value pair on disk in a way to refer to row > J without re-writing the row key or some representation of it? > > Thanks, > Aaron > > On Fri, Aug 10, 2012 at 7:53 PM, Terje Marthinussen > <tmarthinus...@gmail.com> wrote: >> Rowkey is stored only once in any sstable file. >> >> That is, in the spesial case where you get sstable file per column/value, >> you are correct, but normally, I guess most of us are storing more per key. >> >> Regards, >> Terje >> >> On 11 Aug 2012, at 10:34, Aaron Turner <synfina...@gmail.com> wrote: >> >>> Curious, but does cassandra store the rowkey along with every >>> column/value pair on disk (pre-compaction) like Hbase does? If so >>> (which makes the most sense), I assume that's something that is >>> optimized during compaction? >>> >>> >>> -- >>> Aaron Turner >>> http://synfin.net/ Twitter: @synfinatic >>> http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & >>> Windows >>> Those who would give up essential Liberty, to purchase a little temporary >>> Safety, deserve neither Liberty nor Safety. >>> -- Benjamin Franklin >>> "carpe diem quam minimum credula postero" > > > > -- > Aaron Turner > http://synfin.net/ Twitter: @synfinatic > http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & > Windows > Those who would give up essential Liberty, to purchase a little temporary > Safety, deserve neither Liberty nor Safety. > -- Benjamin Franklin > "carpe diem quam minimum credula postero"
