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From Jeremy Hanna <jeremy.hanna1...@gmail.com>
Subject Re: please unsubscribe
Date Fri, 23 Sep 2011 09:48:20 GMT
Vivek - to unsubscribe, look at this link: http://wiki.apache.org/cassandra/FAQ#unsubscribe
On Sep 23, 2011, at 4:40 AM, Vivek Mishra wrote:

>  
>  
> From: Sam Overton [mailto:soverton@acunu.com] 
> Sent: Friday, September 23, 2011 3:09 PM
> To: user@cassandra.apache.org
> Subject: Re: LevelDB type compaction
>  
>  
> On 17 September 2011 00:58, mcasandra <mohitanchlia@gmail.com> wrote:
> >
> >> and updates could be scattered all over
> >> before compaction?
> >
> > No, updates to a given row will be still be in a single sstable.
> 
> Can you please explain little more? You mean that if Level 1 file contains
> range from 1-100 all the updates would still go in that file?
>  
> No, sstables are never written to. All updates go to a memtable, which is then flushed
to a Level0 sstable. Compaction then causes promotion of updates to gradually higher levels.
>  
> The link on leveldb says:
> 
> > The compaction picks a file from level L and all overlapping files from
> > the next level L+1
> 
> If all updates go in the same sstables then how do overlapping files get
> generated. By overlapping I am assuming it means new or updated value for a
> given key exists in multiple files?
>  
> Overlapping refers to the range of keys. The key ranges contained within the files in
any given level represent a set of disjoint intervals (when level >=1). For Level0, the
files may contain overlapping ranges.
>  
> Thanks for the explanation
>  
> Disclaimer: I haven't read the code, this is just my understanding from reading the docs.
>  
>  
> Sam Overton
> Acunu | http://www.acunu.com | @acunu
> 
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