cassandra-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From S Ahmed <>
Subject boonfilters
Date Wed, 07 Apr 2010 20:27:25 GMT
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

  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message