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From "Jeff Jirsa"<jji...@apache.org>
Subject Re: Deflate compressor
Date Thu, 06 Jul 2017 17:27:27 GMT


On 2017-07-06 01:37 (-0700), Cogumelos Maravilha <cogumelosmaravilha@sapo.pt> wrote:

> Hi Jeff,
> 
> Thanks for your reply. But I've already changed from LZ4 to Deflate to 
> get higher compression level. Can I in the Deflate compressor do the 
> same, set for a higher level of compression?


Not at this time; if it's important to you, please open a JIRA (as always, patches from the
community are welcome)


> 
> Another question to the creator of the TimeWindowsCompactionStrategy:
> 
> AND compaction = {'class': 
> 'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy', 
> 'compaction_window_size': '1', 'compaction_window_unit': 'HOURS', 
> 'max_threshold': '128', 'min_threshold': '2'}
> AND compression = {'chunk_length_in_kb': '64', 'class': 
> 'org.apache.cassandra.io.compress.DeflateCompressor'}
> 
> There are some days that I have exactly 24 SSTables:
> ls -alFh *Data*|grep 'Jul  3'|wc
>       24
> Others no:
> ls -alFh *Data*|grep 'Jul  2'|wc
>       59
> 
> Is this normal?

"Maybe", you could use sstablemetadata to get the maxTimestamp from the table, that's what
TWCS will use to group data files together. Keep in mind that repaired sstables won't compact
with unrepaired (if you're using incremental repair), and that tombstone compaction subproperties
(which I don't see in your options, but maybe you had set before) can cause single sstable
compactions that change the timestamp of the FILE, but the data within it may continue to
be much older.

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