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From "Lu, Boying" <Boying...@dell.com>
Subject RE: Some questions to updating and tombstone
Date Tue, 15 Nov 2016 09:05:30 GMT
Thanks a lot for your help.

We are using STCS strategy and not using TTL

Is there any API that we can use to query the current number of tombstones in a CF?



From: Anuj Wadehra [mailto:anujw_2003@yahoo.co.in]
Sent: 2016年11月14日 22:20
To: user@cassandra.apache.org
Subject: Re: Some questions to updating and tombstone

Hi Boying,

I agree with Vladimir.If compaction is not compacting the two sstables with updates soon,
disk space issues will be wasted. For example, if the updates are not closer in time, first
update might be in a big table by the time second update is being written in a new small table.
STCS wont compact them together soon.

Just adding column values with new timestamp shouldnt create any tombstones. But if data is
not merged for long, disk space issues may arise. If you are STCS,just  yo get an idea about
the extent of the problem you can run major compaction and see the amount of disk space created
with that( dont do this in production as major compaction has its own side effects).

Which compaction strategy are you using?
Are these updates done with TTL?

Thanks
Anuj

On Mon, 14 Nov, 2016 at 1:54 PM, Vladimir Yudovin
<vladyu@winguzone.com<mailto:vladyu@winguzone.com>> wrote:
Hi Boying,

UPDATE write new value with new time stamp. Old value is not tombstone, but remains until
compaction. gc_grace_period is not related to this.

Best regards, Vladimir Yudovin,
Winguzone<https://winguzone.com?from=list> - Hosted Cloud Cassandra
Launch your cluster in minutes.


---- On Mon, 14 Nov 2016 03:02:21 -0500Lu, Boying <Boying.Lu@dell.com<mailto:Boying.Lu@dell.com>>
wrote ----

Hi, All,

Will the Cassandra generates a new tombstone when updating a column by using CQL update statement?

And is there any way to get the number of tombstones of a column family since we want to void
generating
too many tombstones within gc_grace_period?

Thanks

Boying

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