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Posted to commits@cassandra.apache.org by "Paulo Motta (JIRA)" <ji...@apache.org> on 2016/12/13 13:40:58 UTC
[jira] [Updated] (CASSANDRA-9792) Reduce Merkle tree serialized
size
[ https://issues.apache.org/jira/browse/CASSANDRA-9792?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Paulo Motta updated CASSANDRA-9792:
-----------------------------------
Assignee: Bharatendra Boddu
> Reduce Merkle tree serialized size
> ----------------------------------
>
> Key: CASSANDRA-9792
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9792
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Bharatendra Boddu
> Assignee: Bharatendra Boddu
> Priority: Minor
> Fix For: 3.0 beta 1
>
> Attachments: MerkleTree.java.patch, Token.java.patch
>
>
> This patch reduces the serialized size of a Merkle Tree by 10%. With num_tokens set to 256, 10% reduction in Merkle tree serialized size for each token range repair, improves network bandwidth during repair
> This table describes serialized sizes (in bytes) of Merkle trees with different depths before and after patch.
> Serialized size of a Merkle tree with certain depth, doesn't depend on number of keys it represent.
> | Depth | Before patch | After patch | Diff |
> |-------+--------------+-------------+-------|
> | 5 | 2060 | 1840 | 220 |
> | 6 | 4044 | 3600 | 444 |
> | 7 | 8012 | 7120 | 892 |
> | 8 | 15948 | 14160 | 1788 |
> | 9 | 31820 | 28240 | 3580 |
> | 10 | 63564 | 56400 | 7164 |
> | 11 | 127052 | 112720 | 14332 |
> | 12 | 254028 | 225360 | 28668 |
> | 13 | 507980 | 450640 | 57340 |
> Merkle tree with depth 15, uses serialized size of ~2MB and with this patch it will be reduce the size by ~200KB. Repairing 256 token ranges will save ~50MB in transfer.
> Also if token serialize() method uses, byte type to represent a token size, then the serialized size can be reduced by 30 to 40%.
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