The old row is accessible and my validation requires a comparison of the two.
JK On Thu, Jul 7, 2011 at 3:23 PM, Yang <teddyyyy...@gmail.com> wrote: > validation is on the new incoming column ,not the old row,right? > On Jul 7, 2011 8:25 AM, "Jeffrey Kesselman" <jef...@gmail.com> wrote: > > Hi Jonnathan, > > > > This brings up an important question. I have been assuming that the > > validation check is part of the atomic update operation. Is this NOT the > > case? Which is to say, can the row be changed between the time the > > validation method is executed and the validated data is written? > > > > The reason I ask is because I have been thinking of this as effectively a > > write-lock on the row during the entire update > > process, including validation, but your answer has caused some concerns > that > > this is wrong... > > > > Thanks > > > > JK > > > > On Thu, Jul 7, 2011 at 2:01 PM, Jonathan Ellis <jbel...@gmail.com> > wrote: > > > >> None of the above, it uses a glorified CAS* at the column level > >> > >> *http://en.wikipedia.org/wiki/Compare-and-swap > >> > >> On Thu, Jul 7, 2011 at 12:51 PM, A J <s5a...@gmail.com> wrote: > >> > Does a write lock: > >> > 1. Just the columns in question for the specific row in question ? > >> > 2. The full row in question ? > >> > 3. The full CF ? > >> > > >> > I doubt read does any locks. > >> > > >> > Thanks. > >> > > >> > >> > >> > >> -- > >> Jonathan Ellis > >> Project Chair, Apache Cassandra > >> co-founder of DataStax, the source for professional Cassandra support > >> http://www.datastax.com > >> > > > > > > > > -- > > It's always darkest just before you are eaten by a grue. > -- It's always darkest just before you are eaten by a grue.
