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From "Tim Estes" <tim.es...@digitalreasoning.com>
Subject Re: boonfilters
Date Wed, 07 Apr 2010 20:29:24 GMT
Bloomfilters I think is what you mean- correct?


Sent from my iPhone

On Apr 7, 2010, at 3:27 PM, "S Ahmed" <sahmed1020@gmail.com> wrote:

> Just reading up on boonfilters, few questions.
>
> Basically boonfilters let give you a true/false if a particular key  
> exists,
> and they *may* give you a false positive i.e. they key exists but  
> never a
> false negative i.e. the key doesn't exist.
>
> The core of boonfilters is its hashing mechanism that marks the in- 
> memory
> matrix/map if the key exists.
>
> 1. Is the only place boonfilters are used in Cassandra is when you  
> want to
> see if a particular key exists in a particular node?
>
> 2. Are boonfilters a fixed size, or they adjust as to the # of  
> keys?  any
> example size?
>
> 3. Boonfilters don't give false negatives:
>    So you hit a node, and perform a lookup in the boonfilter for a  
> key.  It
> says "yes", but when you do a lookup the object returned is null, so  
> then
> you flag that this node needs this particular key during replication.
>
>
> Have I grasp this concept?
>
> Really loving this project, learning allot from the code.  It would  
> be great
> if someone could do a walkthrough of common functionality in a  
> detailed way
> :)

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