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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Hbase/UsingBloomFilters" by JimKellerman
Date Tue, 29 Jul 2008 01:15:28 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The following page has been changed by JimKellerman:
http://wiki.apache.org/hadoop/Hbase/UsingBloomFilters

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+ Bloom filters can be enabled on a per-column family basis in HBase. By specifying true for
the bloom filter parameter in the constructor for H!ColumnDescriptor or by calling H!ColumnDescriptor.setBloomFilter(true),
a [http://portal.acm.org/citation.cfm?id=362692&dl=ACM&coll=portal bloom filter] as
defined by Bloom in 1970 will be added to the column family.
- Bloom filters can be enabled on a per-column family basis in HBase. By specifying true for
the bloom filter parameter in the constructor for HColumnDescriptor or by calling HColumnDescriptor.setBloomFilter(true),
a bloom filter 
-  [http://portal.acm.org/citation.cfm?id=362692&dl=ACM&coll=portal bloom filter]
as defined by Bloom in 1970 will be added to the column family.
  
- Bloom filters can be instantiated by specifying the vector size and the number of hash functions.
 Dynamic bloom filters require an additional argument, a threshold for the maximum number
of keys to record in a row.  
+ This can be done either at table creation time or by disabling the table and modifying the
column through the H!BaseAdmin.modifyColumn API.
  
- Junit testing for these four bloom filters can be found in hbase.regionserver.!TestBloomFilters.
+ Bloom filters are created using the mechanism specified by [http://www.eecs.harvard.edu/~michaelm/NEWWORK/postscripts/BloomFilterSurvey.pdf
Broder and Mitzenmacher] which computes the vector size using 4 hash functions.
  
- '''Additional Resources:'''
+ Junit testing for bloom filters can be found in hbase.regionserver.!TestBloomFilters.
  
-  1. [http://www.cc.gatech.edu/~manolios/bloom-filters/calculator.html Bloom Filter Calculator]
-  1. [http://pages.cs.wisc.edu/~cao/papers/summary-cache/node8.html Bloom Filters - the math]
-  1. [http://www.flipcode.com/articles/article_bloomfilters.shtml Coding Bloom Filters]
- 

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