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From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: nodetool repair and compact
Date Mon, 02 Apr 2018 15:39:32 GMT
Hi,

it will re-write this table's sstable files to current version, while
> re-writing, will evit droppable tombstones (expired +  gc_grace_seconds
> (default 10 days) ), if partition cross different files, they will still
> be kept, but most droppable tombstones gone and size reduced.
>

Nice tip James, I never thought about doing this, it could have been handy
:).

Now, these compactions can be automatically done using the proper tombstone
compaction settings in most cases. Generally, tombstone compaction is
enabled, but if tombstone eviction is still an issue, you might want to
give a try enabling 'unchecked_tombstone_compaction' in the table options.
This might claim quite a lot of disk space (depending on the sstable
overlapping levels).

In case manual action is really needed (even more if it is run
automatically), I would recommend using 'User Defined Compactions' - UDC
(accessible through JMX at least) instead of 'uprade sstable':

- It will remove the tombstones the same way, but with no side effect if
you are currently upgrading for example. If  'upgradesstable' is run as a
routine operation, you might forget about it and suffer consequences.
'upgradesstable' is not only doing the compaction.
- With UDC, you can trigger the compaction of the sstables you want to
remove the tombstones from, instead of compacting *all* the sstables for a
given table.

This last point can prevent harming the cluster with useless compaction,
and even allow the operator to do things like: 'Compact the 10% biggest
sstables, that have an estimated tombstone ratio above 0.5, every day' or
'compact any sstable having more than 75% of tombstones' as you see fit,
and using information such as the sstables sizes and sstablemetadata to get
the tombstone ratio.

C*heers,
-----------------------
Alain Rodriguez - @arodream - alain@thelastpickle.com
France / Spain

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com

2018-04-02 14:55 GMT+01:00 James Shaw <jxyshaw@gmail.com>:

> you may use:  nodetool upgradesstables -a keyspace_name table_name
> it will re-write this table's sstable files to current version, while
> re-writing, will evit droppable tombstones (expired +  gc_grace_seconds
> (default 10 days) ), if partition cross different files, they will still
> be kept, but most droppable tombstones gone and size reduced.
> It works well for ours.
>
>
>
> On Mon, Apr 2, 2018 at 12:45 AM, Jon Haddad <jon@jonhaddad.com> wrote:
>
>> You’ll find the answers to your questions (and quite a bit more) in this
>> blog post from my coworker: http://thelastpickle
>> .com/blog/2016/07/27/about-deletes-and-tombstones.html
>>
>> Repair doesn’t clean up tombstones, they’re only removed through
>> compaction.  I advise taking care with nodetool compact, most of the time
>> it’s not a great idea for a variety of reasons.  Check out the above post,
>> if you still have questions, ask away.
>>
>>
>> On Apr 1, 2018, at 9:41 PM, Xiangfei Ni <xiangfei.ni@cm-dt.com> wrote:
>>
>> Hi All,
>>   I want to delete the expired tombstone, someone uses nodetool repair
>> ,but someone uses compact,so I want to know which one is the correct way,
>>   I have read the below pages from Datastax,but the page just tells us
>> how to use the command,but doesn’t tell us what it is exactly dose,
>>   https://docs.datastax.com/en/cassandra/3.0/cassandra/tools
>> /toolsRepair.html
>>    could anybody tell me how to clean the tombstone and give me some
>> materials include the detailed instruction about the nodetool command and
>> options?Web link is also ok.
>>   Thanks very much
>> Best Regards,
>>
>> 倪项菲*/ **David Ni*
>> 中移德电网络科技有限公司
>>
>> Virtue Intelligent Network Ltd, co.
>> Add: 2003,20F No.35 Luojia creative city,Luoyu Road,Wuhan,HuBei
>> Mob: +86 13797007811 <+86%20137%209700%207811>|Tel: + 86 27 5024 2516
>> <+86%2027%205024%202516>
>>
>>
>>
>

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