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https://issues.apache.org/jira/browse/CASSANDRA-2541?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylvain Lebresne resolved CASSANDRA-2541.
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Resolution: Invalid
Well I was actually wrong in that the splitting reuse the sample as long as it
doesn't have a complete tree (complete in the sens of depth or size greater
that there fixed limits). So I think there is no particular problem here.
There is a small bug in 0.8 code that can make the splitting process exit
early, but I'll open another ticket for that.
> Improve the precision of the repair merkle trees
> ------------------------------------------------
>
> Key: CASSANDRA-2541
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2541
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.6
> Reporter: Sylvain Lebresne
> Assignee: Sylvain Lebresne
> Priority: Minor
> Labels: repair
> Fix For: 0.8.1
>
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> Repair uses the sstable sampled keys to split the merkle tree. This means the
> 'precision' of the tree will be index_interval (so 128 by default). This is
> probably fine when you have lots of skinny rows. But when you have less fat
> rows, this is probably unnecessary imprecise.
> Added to that the fact that each node will not have the same set of samples,
> you may not always end up using the more precise range in the trees when
> computing differences, which could make the imprecision worst (to be fair, it
> is quite possible this happens very rarely).
> Anyway, this ticket proposes to add an additional 'split_factor' (can be
> fixed, can be configurable (by the user or based on metrics on how fat the
> rows are)) that makes use re-split 'split_factor' times each ranges after the
> initial sample-based split of the tree.
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