Yes it will be nice if you can add a parameter in storage-conf.xml to enable write-through to row cache. There are many cases that require the new keys to be immediately available for read. In my case I'm thinking of caching 30-50% of all records in memory to reduce read latency.
Thanks, -Weijun On Tue, Feb 16, 2010 at 5:17 PM, Jonathan Ellis <jbel...@gmail.com> wrote: > On Tue, Feb 16, 2010 at 7:11 PM, Weijun Li <weiju...@gmail.com> wrote: > > Just started to play with the row cache feature in trunk: it seems to be > > working fine so far except that for RowsCached parameter you need to > specify > > number of rows rather than a percentage (e.g., "20%" doesn't work). > > 20% works, but it's 20% of the rows at server startup. So on a fresh > start that is zero. > > Maybe we should just get rid of the % feature... > > > The problem is: when you write to Cassandra it doesn't seem to put the > new > > keys in row cache (it is said to update instead invalidate if the entry > is > > already in cache). Is it easy to implement this feature? > > It's deliberately not done. For many (most?) workloads you don't want > fresh writes blowing away your read cache. The code is in > Table.apply: > > ColumnFamily cachedRow = > cfs.getRawCachedRow(mutation.key()); > if (cachedRow != null) > cachedRow.addAll(columnFamily); > > I think it would be okay to have a WriteThrough option for what you're > asking, though. > > -Jonathan >
