On 2010-05-07 11:03, vineet daniel wrote: > 2. "It is also important for identifying which SSTable files to look inside > even when a key is present." - David can you please throw some more > light on your point, like what are the implications, why do we need to > identify etc.
A bloom filter is almost like a street sign that tells you the range of addresses on a street block. Such a street sign doesn't guarantee the whole range of addresses exists on the block, but it does mean you can avoid driving down streets that don't contain the address you're looking for. When Cassandra is looking for a key, there could be several files that potentially contain it. By looking at the bloom filter for each, it can avoid looking inside the files that definitely do not have the desired data. (My analogy breaks down a bit here because the street signs indicate mutually exclusive ranges of addresses, while the bloom filters may indicate the possible presence of a key in *several* files.) -- David Strauss | da...@fourkitchens.com Four Kitchens | http://fourkitchens.com | +1 512 454 6659 [office] | +1 512 870 8453 [direct]
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