[jira] [Comment Edited] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly
[ https://issues.apache.org/jira/browse/CASSANDRA-12922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=17380536#comment-17380536 ] Branimir Lambov edited comment on CASSANDRA-12922 at 7/14/21, 12:04 PM: To be honest, I did not realize there's a "there is no index file" exit path; an index is required for normal operation. (The only place we can do without one is in {{Scrubber}} which does not rely on {{getPosition}}.) You are right that for the bloom filter not having an index file should not matter, but if such a scenario is to be realized, it would be due to a problem with the index rather than one with the precision of the bloom filter; the relevant data may actually be present. Instead of adding a false positive, I would thus prefer to move the {{ifile == null}} check to the beginning of the method and leave it outside the coverage of the bloom filter tracker. was (Author: blambov): To be honest, I did not realize there's a "there is no index file" exit path; an index is required for normal operation. (The only place we can do without one is in {{Scrubber}} which does not rely on {{getPosition}}.) You are right that for the bloom filter not having an index file should not matter, but if such a scenario is to be realized, it would be due to a problem with the index rather than one with the precision of the bloom filter; the relevant data may actually be present. Instead of adding a false positive, I would thus prefer to move the `ifile == null` check to the beginning of the method and leave it outside the coverage of the bloom filter tracker. > 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 > Components: Legacy/Local Write-Read Paths >Reporter: Branimir Lambov >Assignee: Aleksei Zotov >Priority: Normal > Labels: lhf > Fix For: 3.0.x, 3.11.x, 4.0.x, 4.x > > Attachments: 12922-trunk.txt > > > 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}}. -- This message was sent by Atlassian Jira (v8.3.4#803005) - To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org
[jira] [Comment Edited] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly
[ https://issues.apache.org/jira/browse/CASSANDRA-12922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15685644#comment-15685644 ] Mahdi Mohammadi edited comment on CASSANDRA-12922 at 11/22/16 4:24 AM: --- ||trunk|3.X|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]|[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:12922-3.X]| was (Author: mahdix): ||trunk|3.X|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:12922-3.X]| > 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}}. -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Comment Edited] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly
[ https://issues.apache.org/jira/browse/CASSANDRA-12922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15685644#comment-15685644 ] Mahdi Mohammadi edited comment on CASSANDRA-12922 at 11/22/16 4:24 AM: --- ||trunk||3.X|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]|[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:12922-3.X]| was (Author: mahdix): ||trunk|3.X|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]|[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:12922-3.X]| > 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}}. -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Comment Edited] (CASSANDRA-12922) Bloom filter miss counts are not measured correctly
[ https://issues.apache.org/jira/browse/CASSANDRA-12922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15685644#comment-15685644 ] Mahdi Mohammadi edited comment on CASSANDRA-12922 at 11/22/16 4:23 AM: --- ||trunk|3.X|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:12922-3.X]| was (Author: mahdix): ||trunk|| |[branch|https://github.com/apache/cassandra/compare/trunk...mm-binary:trunk-12922]| > 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}}. -- This message was sent by Atlassian JIRA (v6.3.4#6332)