cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jeffrey Kesselman <jef...@gmail.com>
Subject Re: What does a write lock ?
Date Thu, 07 Jul 2011 19:25:00 GMT
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 <teddyyyy123@gmail.com> wrote:

> validation is on the new incoming column ,not the old row,right?
>  On Jul 7, 2011 8:25 AM, "Jeffrey Kesselman" <jeffpk@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 <jbellis@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 <s5alye@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.

Mime
View raw message