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From Benjamin>
Subject Re: boonfilters
Date Wed, 07 Apr 2010 23:11:55 GMT
Please read this:

On Wed, Apr 7, 2010 at 1:27 PM, S Ahmed <> 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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