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https://issues.apache.org/jira/browse/CASSANDRA-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12920380#action_12920380
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Stu Hood edited comment on CASSANDRA-1608 at 10/12/10 6:33 PM:
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> I guess Cassandra would only need a fixed count of exactly 2, making it a
> non-issue.
As you said: we would need a counting filter with 2 bits per bucket: if both
bits are set, the bucket has collided.
If any of the buckets for a key have collided, you can't perform the delete,
but that isn't the end of the world here.
EDIT: Actually, if you couldn't perform the delete, you might end up
superseding a given sstable multiple times, so this is something we'd want to
avoid.
was (Author: stuhood):
> I guess Cassandra would only need a fixed count of exactly 2, making it a
non-issue.
As you said: we would need a counting filter with 2 bits per bucket: if both
bits are set, the bucket has collided.
If any of the buckets for a key have collided, you can't perform the delete,
but that isn't the end of the world here.
> Redesigned Compaction
> ---------------------
>
> Key: CASSANDRA-1608
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1608
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Chris Goffinet
> Fix For: 0.7.1
>
>
> After seeing the I/O issues in CASSANDRA-1470, I've been doing some more
> thinking on this subject that I wanted to lay out.
> I propose we redo the concept of how compaction works in Cassandra. At the
> moment, compaction is kicked off based on a write access pattern, not read
> access pattern. In most cases, you want the opposite. You want to be able to
> track how well each SSTable is performing in the system. If we were to keep
> statistics in-memory of each SSTable, prioritize them based on most accessed,
> and bloom filter hit/miss ratios, we could intelligently group sstables that
> are being read most often and schedule them for compaction. We could also
> schedule lower priority maintenance on SSTable's not often accessed.
> I also propose we limit the size of each SSTable to a fix sized, that gives
> us the ability to better utilize our bloom filters in a predictable manner.
> At the moment after a certain size, the bloom filters become less reliable.
> This would also allow us to group data most accessed. Currently the size of
> an SSTable can grow to a point where large portions of the data might not
> actually be accessed as often.
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