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Re: TWCS - Disabling Tombstone Compactions for TWCS


That's helpful background, thanks Lerh!  It does seem intentional.

I'd suggest that this violates principal of least surprise (unset defaults
should have the same effect as setting same to default values), and should
be worth calling out as a separate option for both DTCS and TWCS.

On Mon, Jun 4, 2018 at 6:02 PM Lerh Chuan Low <lerh@xxxxxxxxxxxxxxx> wrote:

> Hi Eric,
>
> I think it has something to do with the same reason it is disabled in DTCS:
> https://issues.apache.org/jira/browse/CASSANDRA-9234 can shed more light.
>
>
>
> On 5 June 2018 at 09:02, Eric Stevens <mightye@xxxxxxxxx> wrote:
>
> > I'm trying to understand the reasoning behind this stanza in Time
> Windowed
> > Compaction Strategy's init:
> > https://github.com/apache/cassandra/blob/cassandra-3.0.
> > 15/src/java/org/apache/cassandra/db/compaction/
> > TimeWindowCompactionStrategy.java#L63-L69
> >
> > Reposted (and slightly reformatted) here for convenience:
> > if (
> >
> > !options.containsKey(AbstractCompactionStrategy.
> > TOMBSTONE_COMPACTION_INTERVAL_OPTION)
> > &&
> >
> > !options.containsKey(AbstractCompactionStrategy.
> > TOMBSTONE_THRESHOLD_OPTION)
> > )
> > {
> >     disableTombstoneCompactions = true;
> >     logger.debug("Disabling tombstone compactions for TWCS");
> > }
> > else
> >     logger.debug("Enabling tombstone compactions for TWCS");
> >
> > If you have left both tombstone compaction interval, and tombstone
> > threshold at default values, you are *opting out* of tombstone
> compactions?
> >
> > This was certainly a surprising side effect to us, as we expected unset
> > values to have the same exact effect as setting those values to their
> > defaults.
> >
> > I'm wondering if someone can shed some more light on this, or if this
> > should be considered a bug (it seems really intentional).
> >
>