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From "Yuki Morishita (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-5263) Increase merkle tree depth as needed
Date Thu, 26 Jun 2014 13:52:24 GMT


Yuki Morishita commented on CASSANDRA-5263:

bq. total number of unique partitions in stables containing the range using cardinality

Stored cardinality is for whole SSTable so we cannot use it to estimate cardinality for arbitaly

> Increase merkle tree depth as needed
> ------------------------------------
>                 Key: CASSANDRA-5263
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>    Affects Versions: 1.1.9
>            Reporter: Ahmed Bashir
>            Assignee: Yuki Morishita
>             Fix For: 2.1.1
>         Attachments: 5263-2.1-v1.txt
> Currently, the maximum depth allowed for Merkle trees is hardcoded as 15.  This value
should be configurable, just like phi_convict_treshold and other properties.
> Given a cluster with nodes responsible for a large number of row keys, Merkle tree comparisons
can result in a large amount of unnecessary row keys being streamed.
> Empirical testing indicates that reasonable changes to this depth (18, 20, etc) don't
affect the Merkle tree generation and differencing timings all that much, and they can significantly
reduce the amount of data being streamed during repair. 

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