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https://issues.apache.org/jira/browse/CASSANDRA-9830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15545808#comment-15545808
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Carl Yeksigian commented on CASSANDRA-9830:
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I'm +1 on the code changes to the compaction strategy, but the perf testing
never ran, so we haven't yet shown a reduction in memory usage -
[~pauloricardomg]: can you take a look and ensure it runs (or post the results
if they have run properly).
Also, I'd like to see some additional tests that make sure that we are getting
the same set of results whether or not the bloom filter is loaded for the top
level. Should be both point queries and range queries.
> Option to disable bloom filter in highest level of LCS sstables
> ---------------------------------------------------------------
>
> Key: CASSANDRA-9830
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9830
> Project: Cassandra
> Issue Type: New Feature
> Components: Compaction
> Reporter: Jonathan Ellis
> Assignee: Paulo Motta
> Priority: Minor
> Labels: lcs, performance
> Fix For: 3.x
>
>
> We expect about 90% of data to be in the highest level of LCS in a fully
> populated series. (See also CASSANDRA-9829.)
> Thus if the user is primarily asking for data (partitions) that has actually
> been inserted, the bloom filter on the highest level only helps reject
> sstables about 10% of the time.
> We should add an option that suppresses bloom filter creation on top-level
> sstables. This will dramatically reduce memory usage for LCS and may even
> improve performance as we no longer check a low-value filter.
> (This is also an idea from RocksDB.)
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