cassandra-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Kant Kodali <k...@peernova.com>
Subject Re: If reading from materialized view with a consistency level of quorum am I guaranteed to have the most recent view?
Date Fri, 10 Feb 2017 18:31:34 GMT
yes thanks for the clarification.  But why would I ever have MV with the
same partition key? if it is the same partition key I could just read from
the base table right? our MV Partition key contains the columns from the
base table partition key but in a different order plus an additional column
(which is allowed as of today)

On Fri, Feb 10, 2017 at 10:23 AM, Benjamin Roth <benjamin.roth@jaumo.com>
wrote:

> It depends on your model.
> If the base table + MV have the same partition key, then the MV mutations
> are applied synchronously, so they are written as soon the write request
> returns.
> => In this case you can rely on the R+F > RF
>
> If the partition key of the MV is different, the partition of the MV is
> probably placed on a different host (or said differently it cannot be
> guaranteed that it is on the same host). In this case, the MV updates are
> executed async in a logged batch. So it can be guaranteed they will be
> applied eventually but not at the time the write request returns.
> => You cannot rely and there is no possibility to absolutely guarantee
> anything, not matter what CL you choose. A MV update may always "arrive
> late". I guess it has been implemented like this to not block in case of
> remote request to prefer the cluster sanity over consistency.
>
> Is it now 100% clear?
>
> 2017-02-10 19:17 GMT+01:00 Kant Kodali <kant@peernova.com>:
>
> > So R+W > RF doesnt apply for reads on MV right because say I set QUORUM
> > level consistency for both reads and writes then there can be a scenario
> > where a write is successful to the base table and then say immediately I
> do
> > a read through MV but prior to MV getting the update from the base table.
> > so there isn't any way to make sure to read after MV had been
> successfully
> > updated. is that correct?
> >
> > On Fri, Feb 10, 2017 at 6:30 AM, Benjamin Roth <benjamin.roth@jaumo.com>
> > wrote:
> >
> > > Hi Kant
> > >
> > > Is it clear now?
> > > Sorry for the confusion!
> > >
> > > Have a nice one
> > >
> > > Am 10.02.2017 09:17 schrieb "Kant Kodali" <kant@peernova.com>:
> > >
> > > thanks!
> > >
> > > On Thu, Feb 9, 2017 at 8:51 PM, Benjamin Roth <benjamin.roth@jaumo.com
> >
> > > wrote:
> > >
> > > > Yes it is
> > > >
> > > > Am 10.02.2017 00:46 schrieb "Kant Kodali" <kant@peernova.com>:
> > > >
> > > > > If reading from materialized view with a consistency level of
> quorum
> > am
> > > I
> > > > > guaranteed to have the most recent view? other words is w + r >
n
> > > > contract
> > > > > maintained for MV's as well for both reads and writes?
> > > > >
> > > > > Thanks!
> > > > >
> > > >
> > >
> >
>
>
>
> --
> Benjamin Roth
> Prokurist
>
> Jaumo GmbH · www.jaumo.com
> Wehrstraße 46 · 73035 Göppingen · Germany
> Phone +49 7161 304880-6 · Fax +49 7161 304880-1
> AG Ulm · HRB 731058 · Managing Director: Jens Kammerer
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message