[jira] [Updated] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly

["Mahdi Mohammadi (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-12922?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mahdi Mohammadi updated CASSANDRA-12922:
----------------------------------------
    Status: Patch Available  (was: Open)

> Bloom filter miss counts are not measured correctly
> ---------------------------------------------------
>
>                 Key: CASSANDRA-12922
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12922
>             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|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/io/sstable/format/big/BigTableReader.java#L228].
> This leads to very misleading output from e.g. {{nodetool tablestats}}.



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