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https://issues.apache.org/jira/browse/CASSANDRA-3545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13161263#comment-13161263
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Jonathan Ellis commented on CASSANDRA-3545:
-------------------------------------------
bq. As a compromise I can suggest to apply this patch and add ticket for
feature to cleanup code, move to binary search and new API in ISortedColumns.
I'm afraid that's typically not how we work. If we see a clearly better
approach during review, which this qualifies as, then we'll wait for that
before committing. Especially when the goal is to get into a stable branch.
> Fix very low Secondary Index performance
> ----------------------------------------
>
> Key: CASSANDRA-3545
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3545
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.7.0
> Reporter: Evgeny Ryabitskiy
> Fix For: 1.0.6
>
> Attachments: CASSANDRA-3545.patch, CASSANDRA-3545_v2.patch,
> IndexSearchPerformance.png
>
>
> While performing index search + value filtering over large Index Row ( ~100k
> keys per index value) with chunks (size of 512-1024 keys) search time is
> about 8-12 seconds, which is very very low.
> After profiling I got this picture:
> 60% of search time is calculating MD5 hash with MessageDigester (Of cause it
> is because of RundomPartitioner).
> 33% of search time (half of all MD5 hash calculating time) is double
> calculating of MD5 for comparing two row keys while rotating Index row to
> startKey (when performing search query for next chunk).
> I see several performance improvements:
> 1) Use good algorithm to search startKey in sorted collection, that is faster
> then iteration over all keys. This solution is on first place because it
> simple, need only local code changes and should solve problem (increase
> search in multiple times).
> 2) Don't calculate MD5 hash for startKey every time. It's optimal to compute
> it once (so search will be twice faster).
> Also need local code changes.
> 3) Think about something faster that MD5 for hashing (like
> TigerRandomPartitioner with Tiger/128 hash).
> Need research and maybe this research was done.
> 4) Don't use Tokens (with MD5 hash for RandomPartitioner) for comparing and
> sorting keys in index rows. In index rows, keys can be stored and compared
> with simple Byte Comparator.
> This solution requires huge code changes.
> I'm going to start from first solution. Next improvements can be done with
> next tickets.
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