Also Cassandra working unit is Cells so in a partition there may be possibility of some cells in a row being present in memtable and others may be located in memtable therefore the need of reconciling partition data.
@Jason's point is valid too - User defined timestamp may put sstable cells ahead of memtable ones. Thanks, Bhuvan On Mon, Mar 27, 2017 at 5:29 PM, jason zhao yang < zhaoyangsingap...@gmail.com> wrote: > Hi, > > Cassandra uses last-writetime-win strategy. > > In memory data doesn't mean it is the latest data due to custom write > time, if data is also in Sstable, Cassandra has to read it and reconcile. > > Jasonstack > > On Mon, 27 Mar 2017 at 7:53 PM, 赵豫峰 <zha...@easemob.com> wrote: > >> hello, I get the message that "If the memtable has the desired partition >> data, then the data is read and then merged with the data from the >> SSTables. The SSTable data is accessed as shown in the following steps." >> in "how is data read?" chapter in http://docs.datastax.com/en/ >> archived/cassandra/2.2/cassandra/dml/dmlAboutReads.html. >> >> I do not understand that why have to read SSTable when it has got target >> data in memtable. If the data is in memtable, it means that data is lastest >> one, is there any other reason that it still has to seach in SSTable? >> >> Thanks！ >> >> >> ------------------ >> 赵豫峰 >> >> 环信即时通讯云/研发 >> >> >
