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From "Branimir Lambov (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly
Date Tue, 22 Nov 2016 06:44:58 GMT


Branimir Lambov commented on CASSANDRA-12922:

The fix is ok, but we also need a test. Something like [{{SSTableReaderTest.testGetPositionsKeyCacheStats}}|],
using a small bloom filter or {{AlwaysPresentFilter}} and counting the false positives.

> Bloom filter miss counts are not measured correctly
> ---------------------------------------------------
>                 Key: CASSANDRA-12922
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Branimir Lambov
>            Assignee: Mahdi Mohammadi
> Bloom filter hits and misses are evaluated incorrectly in {{BigTableReader.getPosition}}:
we properly record hits, but not misses. In particular, if we don't find a match for a key
in the index, which is where almost all non-matches will be rejected, [we don't record a bloom
filter false positive|].
> This leads to very misleading output from e.g. {{nodetool tablestats}}.

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