(Should mention: suggesting reading the Dynamo paper for general background, not for Bloom filters, which are fantastically covered in the Wikipedia entry).
On Wed, Apr 7, 2010 at 4:11 PM, Benjamin Black <b...@b3k.us> wrote: > Please read this: > http://www.allthingsdistributed.com/2007/10/amazons_dynamo.html > > On Wed, Apr 7, 2010 at 1:27 PM, S Ahmed <sahmed1...@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 >> :) >> >
