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https://issues.apache.org/jira/browse/CASSANDRA-9673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14717983#comment-14717983
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Stefania commented on CASSANDRA-9673:
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bq. LegacyBatchlogMigrator should log at INFO, conditional on legacy batchlog
table being empty
Do you mean only during migration or all the time? Also, when would we check
that the table is empty: before migrating, after migrating or every time?
bq. LegacyBatchlogMigrator should try and calculate page size from sstable
stats (like LegacyHintsMigrator)
I've applied the logic already available in {{BatchlogManager}}, which is not
the same as {{LegacyHintsMigrator}}. Let me know if the latter is preferable.
bq. Also, there is a bug in LBM::apply: we are calling Batch::createLocal using
the current timestampMicros, whereas we should be using the original create
time. Otherwise we risk to resurrect expired batches here, because of overly
fresh creationTime.
Is it sufficient to multiply the timestamp by 1000 or do we need to dig it out
from the partition update? Not sure how to do this via
{{QueryProcessor.executeInternalWithPaging}}.
Remaining points are done.
> 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
> Labels: performance
> Fix For: 3.0 beta 2
>
> Attachments: 9673_001.tar.gz, 9673_004.tar.gz,
> gc_times_first_node_patched_004.png, gc_times_first_node_trunk_004.png
>
>
> 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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