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https://issues.apache.org/jira/browse/CASSANDRA-9673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14624419#comment-14624419
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Stefania commented on CASSANDRA-9673:
-------------------------------------
[~iamaleksey] can you elaborate a bit more on how to achieve this:
bq. To avoid merely shifting the temp buffer to the receiving side(s) we should
change the structure of the batchlog table to use a list or a map of individual
mutations.
On the receiver, is there a way to do this without deserializing each mutation
only to serialize it again into a blob (byte buffer) or alternatively something
like {{list<mutation_type>}} where {{mutation_type}} is
{code}
ksname : string
key : blob
updates : map<uuid, blob>
{code}
Isn't this worse than just leaving all mutations serialized in a unique byte
buffer copied directly from the incoming message and inserted in the batchlog
table as the data blob?
We could use the {{BufferPool}} to minimize GC, except we just need to find a
way to give the buffers back to the pool eventually.
> Improve batchlog write path
> ---------------------------
>
> Key: CASSANDRA-9673
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9673
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Aleksey Yeschenko
> Assignee: Stefania
> Fix For: 3.0.0 rc1
>
>
> Currently we allocate an on-heap {{ByteBuffer}} to serialize the batched
> mutations into, before sending it to a distant node, generating unnecessary
> garbage (potentially a lot of it).
> With materialized views using the batchlog, it would be nice to optimise the
> write path:
> - introduce a new verb ({{Batch}})
> - introduce a new message ({{BatchMessage}}) that would encapsulate the
> mutations, expiration, and creation time (similar to {{HintMessage}} in
> CASSANDRA-6230)
> - have MS serialize it directly instead of relying on an intermediate buffer
> To avoid merely shifting the temp buffer to the receiving side(s) we should
> change the structure of the batchlog table to use a list or a map of
> individual mutations.
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