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From aaron morton <>
Subject Re: Index interval tuning
Date Wed, 11 May 2011 02:24:05 GMT
What version and what were the values for RecentBloomFilterFalsePositives and BloomFilterFalsePositives

The bloom filter metrics are updated in SSTableReader.getPosition() the only slightly odd
thing I can see is that we do not count a key cache hit a a true positive for the bloom filter.
If there were a lot of key cache hits and a few false positives the ratio would be wrong.
I'll ask around, does not seem to apply to Hectors case though. 


Aaron Morton
Freelance Cassandra Developer

On 11 May 2011, at 10:38, Chris Burroughs wrote:

> On 05/10/2011 02:12 PM, Peter Schuller wrote:
>>> That reminds me, my false positive ration is stuck at 1.0, so I guess
>>> bloom filters aren't doing a lot for me.
>> That sounds unlikely unless you're hitting some edge case like reading
>> a particular row that happened to be a collision, and only that row.
>> This is from JMX stats on the column family store?
> (From jmx)  I also see BloomFilterFalseRatio stuck at 1.0 on my
> production nodes.  The only values that RecentBloomFilterFalseRatio had
> over the past several minutes were 0.0 and 1.0.  While I can't prove
> that isn't accurate, it is very suspicions.
> The code looked reasonable until I got to SSTableReader, which was too
> complicated to just glance through.

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