Really, as i lay in the bath thinking nabout it, I concluded what I am looking for is a very limited form of Consistency.
Its consistency over a single row on a single node just for the period of update. On Thu, Jul 7, 2011 at 10:34 PM, Jeffrey Kesselman <jef...@gmail.com> wrote: > Its not really isolation, btw, because we arent talking about anyone seeing > an update mid-update. Rather, we are talking about when updates are > allowed to occur. > > Atomicity means that all the updates happen together or they don't happen > at all. > Isolation means that no results of the update are visible until the entire > update operation is complete. > > This really lies somewhere in the middle of the two concepts. Its part of > the results of the combined effects of ACID > > > On Thu, Jul 7, 2011 at 10:27 PM, Jonathan Ellis <jbel...@gmail.com> wrote: > >> Sounds to me like you're confusing atomicity with isolation. >> >> On Thu, Jul 7, 2011 at 2:54 PM, Jeffrey Kesselman <jef...@gmail.com> >> wrote: >> > Yup, im even more confused. Lets talk about the model, not the >> > implementation. >> > AIUI updates to a row are atomic across all columns in that row at once, >> > true? >> > If true then the next question is, does the validation happen inside or >> > outside of that guarantee, and is the row guaranteed not to change >> between >> > validation and update? >> > If that is *not* the case then it makes a whole class of solutions to >> > synchronization problems fail and puts my larger project >> > in serious question. >> > >> > On Thu, Jul 7, 2011 at 3:43 PM, Yang <teddyyyy...@gmail.com> wrote: >> >> >> >> no , the memtable is a concurrentskiplistmap >> >> >> >> insertion can happen in parallel >> >> >> >> On Jul 7, 2011 9:24 AM, "Jeffrey Kesselman" <jef...@gmail.com> wrote: >> >> > This has me more confused. >> >> > >> >> > Does this mean that ALL rows on a given node are only updated >> >> > sequentially, >> >> > never in parallel? >> >> > >> >> > On Thu, Jul 7, 2011 at 3:21 PM, Yang <teddyyyy...@gmail.com> wrote: >> >> > >> >> >> just to add onto what jonathan said >> >> >> >> >> >> the columns are immutable . if u overwrite/ reconcile a new obj is >> >> >> created and shoved into the memtable >> >> >> >> >> >> there is a shared lock for all writes though which guard against an >> >> >> exclusive lock on memtable switching/flushing >> >> >> On Jul 7, 2011 7:51 AM, "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. >> >> >> >> >> > >> >> > >> >> > >> >> > -- >> >> > It's always darkest just before you are eaten by a grue. >> > >> > >> > >> > -- >> > It's always darkest just before you are eaten by a grue. >> > >> >> >> >> -- >> 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.
