The ancestors were used primarily to clean up leftovers in the case that
cassandra was killed right as compaction finished, where the
source/origin/ancestors were still on the disk at the same time as the
compaction result.

It's not timestamp based, though - that compaction process has moved to
using a transaction log, which tracks the source/results on a per
compaction basis, and cassandra uses those logs/journals rather than
inspecting the ancestors.

- Jeff



On Thu, Mar 23, 2017 at 4:35 PM, Rajath Subramanyam <rajat...@gmail.com>
wrote:

> Thanks, Jeff. Did all the internal tasks and the compaction tasks move to a
> timestamp-based approach?
>
> Regards,
> Rajath
>
> ------------------------
> Rajath Subramanyam
>
>
> On Thu, Mar 23, 2017 at 2:12 PM, Jeff Jirsa <jji...@gmail.com> wrote:
>
> > That information was removed, because it was really meant to be used for
> a
> > handful of internal tasks, most of which were no longer used. The
> remaining
> > use was cleaning up compaction leftovers, and the compaction leftover
> code
> > was rewritten in 3.0 / CASSANDRA-7066 (note, though, that it's somewhat
> > incomplete in the upgrade case , so CASSANDRA-13313 may be interesting to
> > people who are very very very very very very very sensitive to data
> > consistency)
> >
> >
> > On Thu, Mar 23, 2017 at 2:00 PM, Rajath Subramanyam <rajat...@gmail.com>
> > wrote:
> >
> > > Hello Cassandra-Users and Cassandra-dev,
> > >
> > > One of the handy features in sstablemetadata that was part of Cassandra
> > > 2.1.15 was that it displayed Ancestor information of an SSTable. Here
> is
> > a
> > > sample output of the sstablemetadata tool with the ancestors
> information
> > in
> > > C* 2.1.15:
> > > [centos@chen-datos test1-b83746000fef11e7bdfc8bb2d6662df7]$
> > > sstablemetadata
> > > ks3-test1-ka-2-Statistics.db | grep "Ancestors"
> > > Ancestors: [1]
> > > [centos@chen-datos test1-b83746000fef11e7bdfc8bb2d6662df7]$
> > >
> > > However, the same tool in Cassandra 3.0.x no longer gives us that
> > > information. Here is a sample output of the sstablemetadata grepping
> for
> > > Ancestors information in C* 3.0 (the output is empty since it is no
> > longer
> > > available):
> > > [centos@rj-cassandra-1 elsevier1-ab7389f0fafb11e6ac23e7ccf62f494b]$
> > > sstablemetadata mc-5-big-Statistics.db | grep "Ancestors"
> > > [centos@rj-cassandra-1 elsevier1-ab7389f0fafb11e6ac23e7ccf62f494b]$
> > >
> > > My question, how can I get this information in C* 3.0.x ?
> > >
> > > Thank you !
> > >
> > > Regards,
> > > Rajath
> > >
> > > ------------------------
> > > Rajath Subramanyam
> > >
> >
>

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