but a compaction will mutate the sstables and reclaim the space (eventually) ?
james On 18 Feb 2011, at 08:36, Sylvain Lebresne wrote: > On Fri, Feb 18, 2011 at 8:14 AM, Aklin_81 <asdk...@gmail.com> wrote: > Are the very freshly written columns to a row in memtables, efficiently > updated/overwritten by edited/new column values. > > After flushing of memtable, are those(edited + unedited ones) columns stored > together on disk (in same blocks!?) as if they were written in one single > operation or same time ?? I know if old columns are edited then several > copies of same column will be dispersed in different sst tables, what about > fresh columns ? > > Are there any disadvantages to frequently updating fresh columns present in > memtable ? > > The SSTables are immutable but the memtable are not. As long as you > update/overwrite a column that is still in memtable, it is simply replaced in > memory (so it's as efficient as it gets). > In other words, when the memtable is flushed, only the last version of the > column goes in. > > -- > Sylvain
